山推 BYD4208 变速箱维修手册
山推 BYD4208 变速箱维修手册
BS428 Transmission Service Manual
Foreword
This service manual mainly covers the removal and refitting process, service technology and
standard requirements for BS428 transmission (also applies to BYD4208 series transmission), so as
to help service personnel understand the method of removing and refitting it and to lay a solid
technical foundation for them concerning proper fault diagnosis and troubleshooting.
This service manual mainly includes the following:
Chapter 1 Introduction
This chapter mainly describes precautions for servicing transmission, explains the meaning of each
symbol which are included in the following text and specifies the tightening torque for plain bolts.
Chapter 2 Transmission system
This chapter mainly describes the gearshift principle of transmission, the transmission line of each
gear, and the operation and maintenance of oil supply line and transmission.
Chapter 3 Removal of transmission
This chapter describes how to remove each part properly and the relevant precautions in the
process.
Chapter 4 Refitting of transmission
This chapter describes how to refit each part properly and the relevant precautions in the process.
Chapter 5 Service tools for transmission
This chapter describes special tools required in the process of servicing transmission.
Chapter 6 Fault diagnosis and troubleshooting
This chapter describes common faults and troubleshooting of the transmission.
Note
The specifications of parts covered by this Manual may be subject to modification due to the
improvement of this product, and no further notice will be given upon such modification, so
please contact SDLG for the latest data.
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Contents
1 Introduction ................................................................................................................ 1
1.1 Safety precautions ............................................................................................. 1
1.2 Description of signs ........................................................................................... 2
1.3 Tightening torque table for plain bolts .............................................................. 3
2 Transmission system .................................................................................................. 5
2.1 Description of transmission ............................................................................... 5
2.2 Basic parameters of transmission & torque converter assembly ...................... 6
2.3 Structure and principle of transmission ............................................................. 6
2.3.1 Structure of transmission ........................................................................... 6
2.3.2 Shifting principle of transmission .............................................................. 7
2.3.3 Gear transmission lines .............................................................................. 8
2.3.4 Structure and principle of shifting clutch ................................................ 10
2.3.5 Structure and principle of automatic emptying valve (oil drain valve) ... 11
2.4 Oil supply system ............................................................................................ 13
2.4.1 Structure and working principle of transmission & torque converter oil
supply system .................................................................................................... 13
2.4.2 Introduction to oil supply system main components ............................... 14
2.5 Transmission Operation and Maintenance ...................................................... 18
2.5.1 Installation and Application Notices for Transmission ........................... 18
2.5.2 Maintenance of Transmission .................................................................. 18
3 Removal of Transmission ......................................................................................... 20
3.1 Removal of assembly components .................................................................. 20
3.1.1 Removal of oil filler pipe and filter ......................................................... 20
3.1.2 Removal of parking brake assembly ....................................................... 21
3.1.3 Removal of transmission control valve ................................................... 22
3.1.4 Removal of breather and cover plate ....................................................... 23
3.1.5 Removal of input flange .......................................................................... 23
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3.1.6 Removal of oil sump ................................................................................ 23
3.1.7 Removal of high/low gearshift fork mechanism ..................................... 24
3.1.8 Removal of output shaft ........................................................................... 24
3.1.9 Removal of three sets of clutch gear shafts ............................................. 26
3.2 Removal of assembly ...................................................................................... 28
3.2.1 Removal of transmission control valve ................................................... 28
3.2.2 Removal of three sets of clutch gear shaft assemblies ............................ 30
4 Refitting of Transmission ......................................................................................... 34
4.1 Refitting of assembly ....................................................................................... 34
4.1.1 Refitting of clutch shaft assembly ........................................................... 34
4.2 Refitting of assembly components .................................................................. 38
4.2.1 Assembly of three sets of gear shafts ....................................................... 38
4.2.2 Refitting of input flange and rear end cover ............................................ 40
4.2.3 Assembly of countershaft and reverse gear shaft rear end cover ............ 41
4.2.4 Assembly of output shaft ......................................................................... 42
4.2.5 Assembly of high/low gearshift fork mechanism .................................... 42
4.2.6 Assembly of oil sump .............................................................................. 43
4.2.7 Assembly of transmission control valve .................................................. 43
4.2.8 Assembly of breather and cover plate ...................................................... 44
4.2.9 Assembly of parking brake assembly ...................................................... 44
4.2.10 Assembly of oil filler pipe and filter ...................................................... 45
5 Service Tools for Transmission ................................................................................ 46
6 Common Fault Diagnosis and Troubleshooting ....................................................... 47
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1 Introduction
1.1 Safety precautions
Important safety notice
Service and maintenance is essential to the safe operation of vehicle. This Manual mainly
states the related techniques on how to remove and refit the transmission assembly properly.
To prevent relevant personnel from being hurt, this Manual takes as safety sign. With
regard to precautions attached with this sign, it is required to do operation carefully. In case
of potential hazard, first take into account the safety of yourself, and meanwhile take
necessary protective measures.
Safety notice
In the process of refitting and removal, improper operation technique will lead to part damage,
service life reduction and deterioration in operating performance, and in addition, it may cause
unsafe factors. Therefore, please read related content in this manual carefully before refitting and
removing any part.
1. The parameters, figures and content covered by this manual apply to product of standard
configuration. As regard to variant, please consult our coMPany or relevant data.
2. In repair workshop, a separate or special area shall be set for placing removed parts,
corresponding tools and parts shall be placed at appropriate area, and the operation area shall be
kept clean and free of oil dirt and other contaminant. Do not smoke at any place other than the
specified area. Never smoke during operation, and it is required to have fire extinguishing device.
3. When welding operation is necessary, it shall be done by a trained and experienced welding
worker. During welding, it is required to wear and use appropriate protective equipment such as
welding gloves, baffle, goggles, work cap and overall.
4. Before removing transmission & torque converter assembly, make sure to clean the dirt from its
external surface so as to prevent parts from being contaminated during removal.
5. During operation, do wear safety shoes and safety helmet. Do not wear inappropriate work coat.
The work coat must be buttoned. When striking parts with a copper rod, safety goggles shall be
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worn.
6. Petrol, kerosene and water-based oil cleaner can be used to clean the removed parts.
7. To use a crane or other hoisting equipment, first check the slings for damage. It is required to use
hoisting equipment with sufficient lifting capacity. During lifting operation, do lift slowly at
appointed position so as to prevent parts from striking against each other. Do not work under the
lifted parts.
8. When two or more people are required to work simultaneously, they shall be in agreement with
the same operation procedure in advance to avoid accident due to out of step conditions.
9. Make sure to keep all tools properly and get familiar with their operating methods.
10. To align one hole with another, do not get your hand or finger into the holes. As regards to parts
requiring direct assembly with hand, always pay attention to the holding position and check it for
risk of crushing.
11. Make sure to perform inspection on the removed parts. The part of which the defect has already
affected the performance must be replaced.
12. After assembling all parts, no interference is allowed.
13. When assembling the oil seal and seal ring, if they have to pass key groove, screw hole and step,
then corresponding protective measures shall be taken so as to avoid damaging them.
14. In the process of refitting parts, the tools used shall match corresponding threaded fasteners so
as to prevent the fasteners from being damaged.
15. To tighten joint body and plug screw, do not use pneumatic wrench. Be sure to rotate them to
some extent with hand, and then tighten them with torque wrench of corresponding specification to
the required torque value.
16. When draining oil from transmission, be sure to unscrew the drain plug slowly so as to prevent
oil from spurting out.
1.2 Description of signs
To make this manual fully play its roles, the signs in Table 1-1 are used in respect of critical safety
and quality requirements.
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Table 1-1
Sign
Item Remarks
Safety
During operation, pay special attention to safety.
During operation, pay special attention to safety because of
inside pressure.
Note
During operation, pay special attention to technical
requirements so as to ensure operation quality.
Weight
Weight of component or device and removal & refitting modes.
Pay attention to the selection of sling and the postures during
operation.
Tightening
torque
Pay special attention to the tightening torque of component
during assembly.
Application Points requiring the application of adhesive and grease.
Oil and water Add a certain amount of oil, water and fuel.
Draining Position for draining oil or water, as well as draining amount.
1.3 Tightening torque table for plain bolts
Table 1-2
Strength
class
Yield
strength
(N/mm2)
Nominal diameter of bolt (mm)
6 8 10 12 14
Tightening torque (Nm)
8.8 640 9~12 22~30 45~59 78~104 124~165
10.9 900 13~16 30~36 65~78 110~130 180~210
12.9 1080 16~21 38~51 75~100 131~175 209~278
Strength
class
Yield
strength
(N/
Nominal diameter of bolt (mm)
16 18 20 22 24
Tightening torque (Nm)
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mm2)
8.8 640 193~257 264~354 376~502 521~683 651~868
10.9 900 280~330 380~450 540~650 740~880 940~1120
12.9 1080 326~434 448~597 635~847 864~1152 1098~1464
Strength
class
Yield
strength
(N/
mm2)
Nominal diameter of bolt (mm)
27 30 33 36 39
Tightening torque (Nm)
8.8 640 952~1269 1293~1723 1759~2345 2259~3012 2923~3898
10.9 900 1400~1650 1700~2000 2473~3298 2800~3350 4111~5481
12.9 1080 1606~2142 2181~2908 2968~3958 3812~5082 4933~6577
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2 Transmission system
2.1 Description of transmission
BS428 transmission is a fixed shaft, constant mesh and power gearshift transmission, which is
mainly used for LG933L and LG936L loader. In the transmission system of LG933L and LG936L,
the engine is directly connected to the torque converter via an elastic plate so as to realize output
power, and torque converter is connected via the propeller shaft to front input flange of the
transmission where speed change and torque increase happens such that the power can be
transmitted to front and rear drive axles via front and rear propeller shafts respectively.
BS428 transmission mainly consists of input shaft assembly, countershaft assembly, and reverse
gear shaft assembly, high-low gear sliding sleeve as well as its control mechanism and many pairs
of constant mesh gear, etc.
Fig. 2-1
1.Breather 2.Transmission control valve 3.Reverse gear shaft 4. Input shaft 5.Countershaft
6.Oil drain plug 7.High-low gearshift fork 8.Output shaft 9.Filter 10.Oil filler pipe
11.Parking brake
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2.2 Basic parameters of transmission & torque converter assembly
Table 2-1
Item Parameters/description
Torque
converter
Type Single-stage three-element turbine hydraulic
torque converter
Torque ratio 3.25
Oil pressure at torque converter inlet
(MPa) 0.5~0.6
Oil pressure at torque converter
outlet (MPa) 0.2~0.3
Transmission
Type Fixed-shaft power shift
Gears 4 gears in front and 2 in the rear
Transmission working pressure
(MPa) 1.1~1.5
2.3 Structure and principle of transmission
2.3.1 Structure of transmission
BS428 transmission includes three sets of normally opened clutches, which are closed by hydraulic
fluid, and they control the 1st gear, 2nd gear, 1st reverse gear respectively, or the 3rd gear, 4th gear
and 2nd reverse gear when the shift fork is set to a higher gear. The one installed on the input shaft
is the 1st gear clutch; the power from torque converter is transmitted to input shaft via a connecting
flange and the input shaft is the total input of transmission. The one installed on the countershaft is
the 2nd gear clutch, and the countershaft can transmit the power from the 1st gear and the reverse
gear to the output gear. The one installed on the reverse gear shaft is the reverse gear clutch which
can make the loader drive backwards when it is engaged.
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Fig. 2-2
1. Reverse gear shaft clutch 2. Input shaft clutch 3. Intermediate gear shaft clutch
2.3.2 Shifting principle of transmission
The transmission’s gearshift mechanism is a mechanically-operated one, with the gear controller of
BS428 transmission shown in Fig.2-3. This gear controller includes two gearshift levers: 1.
direction control handle (see Fig. on the left), which connects to the gearshift control valve stem on
the transmission via a flexible shaft; 2. high/low speed control handle (see Fig. on the right), which
connects to the shift fork on the transmission via a flexible shaft. The gear controller operates the
clutches of different gears by controlling the speed change valve. The working conditions of
clutches are shown in table 2-2.
Fig. 2-3 Gear selector
View from input terminal Input shaft
Reverse gear shaft
Countershaft
Output shaft
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Table 2-2 Working conditions of clutches
Ⅰ Ⅱ Ⅲ Shift fork
Ⅰ √
Ⅱ √
Ⅲ √
Ⅳ √
Ⅰ √
Ⅱ √
2.3.3 Gear transmission lines
The power of the hydraulic torque converter is transmitted to the transmission via the input shaft
flange installed on the part of the right end of the input shaft that extends outside the transmission
box. The input shaft assembly, reserve gear shaft assembly and immediate shaft assembly connects
with the transmission box in the same way. Both ends of them are supported on the transmission
box and big end cap by conical bearings. Adjust the clearance of conical bearing during assembly,
to avoid damage to the bearing. The gears on the output shaft assembly, reverse gear shaft assembly,
countershaft assembly and output shaft are constantly meshed with each other. There are three stop
positions (HI, N, LO) in the high-low gear sliding sleeve which is refitted on the output shaft. The
high gear position corresponds to a high speed; the low gear position corresponds to a low speed.
When the sliding sleeve stays at the neutral position, no power will be output by the transmission.
Caution: Never shift the high-low gear sliding sleeve before the transmission is in the
neutral gear after the loader is stationary, otherwise, impacting and crashing of the gears may
occur.
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1. 1st (3rd) gear transmission line
Fig. 2-4
3rd gear (when the shift fork is set to the right
high speed gear):
input→Z3→Z4→Z7→Z9→output
1st gear (when the shift fork is set to the left
low speed gear):
input→Z3→Z4→Z7→Z5→Z8→Output
2. 2nd (4th) gear transmission line
Fig. 2-5
4th gear (when the shift fork is set to the right
high speed gear): input→Z3→Z6→Z7→Z9→
output
2nd gear (when the shift fork is set to the left
low speed gear): input→Z3→Z6→Z5→Z8→
output
3. 1st (2nd) reverse gear transmission line
1nd reverse gear (when the fork is set to the left
low speed gear): input→Z3→Z1→Z2→Z7→
Z5→Z8→output
2nd reverse gear (when the fork is set to the
right high speed gear): input→Z3→Z1→Z2→
Z4→Z7→Z9→output
Reverse gear shaft
Input shaft
Countershaft
Output shaft
Reverse gear shaft
Input shaft
Countershaft
Output shaft
Reverse gear shaft
Input
shaft Countershaft
Output shaft
Input shaft
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Fig. 2-6
2.3.4 Structure and principle of shifting clutch
1. Structure
The housing and gear of the hydraulic clutch is fixed together with bolts, and the gear connects to
the external spline of the propeller shaft via the internal spline, all of which consist of the driving or
driven part of the clutch. The inner part of the clutch consists of piston, outer friction lining, inner
friction lining, oil seal ring, return spring, outer end cover, retaining ring, etc. The driving friction
lining of the clutch connects to the clutch housing via the external spline, and the driven friction
lining of the clutch connects to the external spline of the gear via the internal friction lining.
Another gear is supported on the propeller shaft by the bearing and can rotate with respect to the
propeller shaft.
The outer friction linings in three sets of clutches are copper based powder metallurgy friction
linings (6 PCS for each). The internal friction linings are made of 65Mn (5 PCS for each), with 0.5
mm concavity. When assembling, the convex surface shall face the piston end and make sure to
rotate the friction linings manually after assembly for inspection.
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Fig. 2-7
1. Constant mesh gear 2. Centrifugal emptying valve 3. Clutch housing 4. Piston
5. Driving friction lining 6. Driven friction lining 7. Driven gear 8. Spring 9. Piston ring
10. Cylinder oil inlet passage 11. Lubricating oil passage 12. Seal ring
2. Working principle
When working: the transmission oil from the transmission control valve flows through the oil
passage in the transmission box and the big end cap and to the cylinder via the inlet end cover and
clutch shaft that will make the piston move forward, compress the driving and driven clutch plates,
and output the power via the driven gear that has been integrated with the clutch housing.
When stop working: The pressure oil will be cut off; the transmission oil in the cylinder returns via
the oil port; the piston returns via the return spring; the driving and driven clutch plates separates
and the gear idles.
2.3.5 Structure and principle of automatic emptying valve (oil drain valve)
After the clutch cylinder cut off the oil supply, the clutch housing will continue to rotate with the
shaft under the action of inertia force, and the transmission oil in the cylinder will move from the
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inside to the outside under the action of centrifugal force which will generate pressure at the
circumferential edge of the cylinder and a thrust for the poison return, therefore hindering the rapid
separation of the clutch. In order to remove the centrifugal pressure from the oil inside the rotating
cylinder, an automatic emptying valve shall be set on the clutch housing.
Fig. 2-8
1 Piston 2 Clutch cylinder 3 Steel ball
When the clutch is engaged:
The pressure oil flows into the cylinder and flows out from the oil drainage hole via the pore
passage between the steel ball and the pore. At this point, pressure difference will be formed at the
front and the back of the steel ball. Under the action of this pressure difference, the steel ball will be
pushed to the oil drainage hole to cover it. When the oil drainage stops, the oil pressure in the
cylinder will rise.
When the clutch is released:
The cylinder connects with the return oil passage to release the pressure. At this point, the steel ball
will no longer be pushed by the pressure oil and will move outward under the action of the
centrifugal force, then, the oil drainage hole will open. The oil in the cylinder flows out from the oil
drainage hole via the pore passage between the steel ball and the pore, which will help the quick
return of the cylinder piston.
When the clutch is engaged When the clutch is released
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2.4 Oil supply system
2.4.1 Structure and working principle of transmission & torque converter
oil supply system
1. Structure of oil supply system
The oil supply system is an important component of the hydro-mechanical transmission system,
which generally consists of transmission pump, transmission control valve, oil filter, radiator, oil
pan and pipeline, etc.
Fig. 2-9 Composition of oil supply system
1. Relief valve 2. Secondary filter 3. Transmission pump 4. Torque converter
5. Radiator 6. Speed change valve 7. Oil pan 8. Primary filter
2. Working principle of oil supply line
When the pump impeller of the torque converter is running, the driving gear will drive the operation
of the oil pump to suck oil from the tank and output the pressure oil, which will flow into the torque
converter combination valve. The torque converter combination valve consists of transmission
pressure valve, inlet pressure valve and constrictor. The working oil to the combination valve
ensures sufficient oil for operation first and then is transmitted to the torque converter via the
transmission pressure valve under the action of the transmission pressure valve. The oil pressure for
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transmission control and the oil pressure at torque converter inlet are controlled by the transmission
pressure valve and inlet pressure valve, with oil pressure of 1.1~1.5 MPa and 0.5~0.6 MPa
respectively. If the oil pressure at torque converter inlet exceeds the setting value of the inlet
pressure valve, the valve port will open and the oil will spill out for oil spray of the transmission
and the torque converter. Torque converter outlet pressure valve will keep the pressure at torque
converter outlet within 0.05~0.15 MPa. The oil from the outlet pressure valve will flow through the
radiator to the transmission lubrication system.
Fig. 2-10 Schematic diagram for the oil supply of transmission & torque converter system
2.4.2 Introduction to oil supply system main components
1. Structure and working principle of hydraulic torque converter
YJ315LG-1 hydraulic torque converter is a single-stage single-phase three-element hydraulic torque
converter. This series of torque converter as shown in Fig. 2-11 consist of energy conversion
elements (impeller, turbine, guide pulley), power input/output elements (elastic plate,wheel cover,
turbine shaft, output flange), fixed supporting element (housing), hydraulic parts and other
accessories, etc.
Inlet pressure valve
Torque converter
combination valve
Torque converter
Transmissi
on pressure
valve
Cooler
Lubrication Shower
1st and 3rd gear clutch 2nd and 4th gear
clutch
Reverse gear clutch
Reverse gear
Neutral gear
1st and 3rd gear
2nd and 4th gear
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Fig. 2-11 Structure and schematic diagram of torque converter
1. Elastic plate 2. Turbine 3. Impeller 4. Guide pulley
5. Guide pulley seat 6. Turbine shaft 7. Output flange.
(1) Power input part
The drive plate, wheel cover and impeller constitute the power input part of the torque converter.
The wheel cover connects with the drive plate via rubber damping block or elastic plate, and the
drive plate connects with the engine flywheel housing via screws.
When the engine is running, the flywheel will drive the rotation of wheel cover via the drive plate.
The wheel cover is firmly connected to the impeller with bolts and sealed at the joint surface with
O-rings. One end of the input part is supported on the center hole of the diesel engine flywheel
housing by the shaft end of the wheel cover, and the other end is supported on the guide pulley seat
by the bearing of impeller.
YJ315LG-1 torque converter has also been equipped with PTO port. A part of power from the diesel
engine is directly transmitted to the pump shaft gear via the transfer gear refitted on the impeller
and drives the operation of gear pump by the pump shaft, etc.
(2) Power output part
The turbine, driving shaft, driving gear, output gear and output shaft together constitute the power
output part of the torque converter. The turbine output shaft is supported at two points. That’s, the
left end is supported on the torque converter wheel cover by needle roller bearing, and the right end
is supported on the torque converter housing by ball bearing. The power from turbine output shaft is
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transmitted via driving gear to the output gear with which the driving gear is meshed, and then to
the output shaft by the output gear.
(3) Fixed supporting part of guide pulley
Guide pulley is fixed on the guide pulley seat via the splined joint, and the guide pulley seat is fixed
on the torque converter housing with screws.
(4) Sealing part of circulating circle
YJ315LG-1 hydraulic torque converter uses three kinds of seals:
● O-ring is used at the joint of wheel cover and impeller to prevent the leakage of liquid in the
circulating circle along the joint.
● Alloy cast iron seal ring is used between the impeller hub and the guide pulley seat to prevent
the leakage of oil at the bearing seat.
● Skeleton oil seal is used at the middle part of flywheel housing and the impeller hub. Note that
the lips of the skeleton oil seal shall face to the incoming flow when assembling.
2. Transmission control valve
The transmission control valve is mainly composed of speed change valve and power shut-off valve,
etc. When pulling the speed change valve lever outwards to the limit, the reverse gear will be
engaged, and when pushing it inwards, neutral gear, 1st gear and 2nd gear will be engaged
successively. The valve body has also been equipped with power shut-off valve, which will shut off
the power oil to the transmission during braking to ensure more reliable braking performance.
Fig. 2-12 Transmission control valve
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1. Power shut-off valve 2. Main pressure measuring port 3. Speed change valve oil inlet
4. Speed change valve lever 5. 1st and 3rd gear lubricating oil passage 6. 1st and 3rd gear
pressure oil passage 7. 2nd and 4th gear pressure oil passage 8. 2rd and 4th gear lubricating oil
passages 9. Reverse gear lubricating oil passage 10. Reverse gear pressure oil passage
11. Oil sprayer port 12. Cooling oil port
(2) Relief valve
The relief valve is mainly composed of transmission pressure valve and torque converter inlet
pressure valve, etc. The speed change valve controls the transmission control pressure (1.1~1.5
MPa); the torque converter inlet pressure valve controls the torque converter inlet oil pressure
(0.5~0.6 MPa). The relief valve is equipped with an oil passage which can be used to lubricate the
torque converter internal gear. When the oil supply pressure in the system is too high, the overflow
valve in the relief valve will open and release pressure via the pressure relief vent.
Fig. 2-13 Relief valve
1. Pressure adjusting bolt 2. Pressure relief vent 3. Lubricating oil port of torque converter
internal gear 4. Torque converter oil inlet 5. Overflow valve 6. Transmission control valve oil
inlet 7. Relief valve oil inlet 8. Torque converter inlet oil pressure adjusting bolt
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2.5 Transmission Operation and Maintenance
2.5.1 Installation and Application Notices for Transmission
(1) When installing transmission, ensure the input share the same axis with the torque converter
output and the transmission output share the same axis with the input of front/rear axle.
(2) Transmission, after installed to the vehicle, shall be filled with about 45L of 6# hydraulic
transmission oil from oil filler, and the oil level shall be checked 5 min after starting the engine,
which shall reach to the level of oil dipstick. Before and after working every shift, always check the
oil level in the transmission carefully.
(3) The gear change in transmission from forward gear to reverse
gear or vice versa as well as between high and low gears must be
carried out after parking, but the change between 1st and 2
nd gear or
between 3rd
and 4th
gear can be done while driving.
(4) Attention shall be paid to maintain the operating oil pressure at
1.1~1.5MPa during transmission operation, and the outlet oil
temperature of torque converter shall be generally not more than
105°C and will not exceed 115°C in the short run, together with the
oil temperature at the transmission oil sump not larger than 100°C.
(5) Each control handle and mechanism shall be flexible without
seizure, and gearshift must be accurate with obvious tactility.
(6) When depressing the brake pedal with engine throttle full open,
the vehicle shall not move.
(7) Appropriate adjustment must be done to parking brake to make
sure it will work reliably.
Fig. 2-14
2.5.2 Maintenance of Transmission
(1) Change oil in the transmission of new vehicle for the first time after the vehicle travels for 100 h
and thereafter perform this operation every 500 h. The oil to be filled shall be 6# (8#) hydraulic
transmission oil with filling amount of about 38L; the oil level shall be checked within 5 min after
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the engine is started and then runs at idling, and the level of oil dipstick shall apply. Before and after
working every shift, always check the oil level in the transmission carefully.
(2) Attention shall be paid to maintain the operating oil pressure at 1.1~1.5MPa during transmission
operation, and the outlet oil temperature of torque converter shall be generally not more than 105°C
and will not exceed 115°C in the short run.
(3) New transmission, after installed to the vehicle, shall experience 12 h running-in, 2 h for each
gear, and the load during which shall not exceed 70% of rated load. Meanwhile, note the oil
temperature, oil level and the fastening of bolts. After the period of running-in, wash transmission
oil sump and the oil filter screen.
(4) The gear change in transmission from forward gear to reverse gear or vice versa as well as
between high and low gears must be carried out after the vehicle is stopped, but the gear change
between 1st and 2
nd gear or between 3
rd and 4
th gear can be done while the vehicle is running.
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3 Removal of Transmission
3.1 Removal of assembly components
Preparation for removal:
(1) Fully clean the mud and dirt on the transmission.
(2) Remove drain plug to drain transmission oil.
Hydraulic transmission oil: about 45L.
(3) Prepare a stable transmission mounting bracket.
Transmission: about 200Kg
3.1.1 Removal of oil filler pipe and filter
Fig. 3-1
1 Oil dipstick 2 Oil filler pipe
3 Bolt
1. Remove oil dipstick and the bolts fastening oil
filler pipe and transmission body, and then
disassemble oil filler pipe and O-ring.
NOTE:
Protect O-ring.
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Fig. 3-2
1 Filter
2. Disassemble filter housing, and remove O-ring,
6 bolts, filter cover and shim.
Fig. 3-3
1 Filter element
3. Take filter element out.
Fig. 3-4
1 Parking brake
2 Fixing bolt
3.1.2 Removal of parking brake
assembly
1. Disassemble the bolts connecting parking
brake and transmission body to take down the
parking brake.
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Fig. 3-5
1 Lock plate
2 Bolt
2. Disassemble the lock plate and fixing bolts
from rear front output flange; remove pressure
plate and O-ring.
Fig. 3-6
1 Oil seal cover 2 Oil seal
3 Output shaft flange 4 Dust cover
5 Brake caliper & disc
3. Remove output shaft flange, brake caliper &
disc and dust cover with hands. Disassemble
the bolts connecting oil seal cover and
transmission body, remove oil seal cover and
adjusting shim and take out oil seal from oil
seal cover.
Fig. 3-7
1 Bolt
2 Transmission control valve
3.1.3 Removal of transmission control
valve
1. Disassemble the bolts connecting transmission
control valve and transmission, and then
remove upper paper washer, bottom plate and
lower paper washer in turn.
NOTE:
● Ensure cleanness and protection after
removing the transmission control valve.
BS428 Transmission Service Manual
23
● Protect sealing surface and gasket.
Fig. 3-8
1 Bolt 2 Cover plate
3 Breather
3.1.4 Removal of breather and cover
plate
1. Disassemble breather and take out flap, copper
pipe and 5 Labyrinth gaskets.
Disassemble connecting bolts from the cover plate
to remove paper washer.
Fig. 3-9
1 Round nut 2 Round nut washer
3 Washer
3.1.5 Removal of input flange
1. Disassemble round nuts from input shaft with a
special socket to remove round nut washer, washer,
input flange and dust cover.
Fig. 3-10
1 Bolt
2 Oil sump
3.1.6 Removal of oil sump
1. Lay transmission body sideways, and
disassemble the bolts connecting oil sump and
transmission body to remove the oil sump.
BS428 Transmission Service Manual
24
Fig. 3-11
1 Iron wire 2 Fastening screw
3 Fork shaft
3.1.7 Removal of high/low gearshift
fork mechanism
1. Disassemble the iron wire on high/low
gearshift fork mechanism, unscrew fastening
screws and remove fork shaft and the fork.
Fig. 3-12
1 Bolt
2. Unscrew screw plug and washer, remove steel
balls and spring and then disassemble oil seal.
Fig. 3-13
1 Lock plate 2 Bolt
3 Pressure plate 4 Output shaft flange
3.1.8 Removal of output shaft
1. Disassemble lock plate, unscrew the fixing
bolts of rear output flange, remove pressure
plate and O-ring and then take out the output
shaft flange, dust cover and oil seal by hand.
NOTE:
Protect O-ring.
BS428 Transmission Service Manual
25
Fig. 3-14
1 Bolt
2 Output rear end cover
2. Unscrew the bolts connecting output rear end
cover to transmission body, disassemble output
rear end cover and take it out together with the
whole output shaft backwards.
Fig. 3-15
1 Output shaft 2 Thrust ring
3 Gear (output shaft high gear) 4 High/low
gear sliding sleeve
5 Gear (output shaft low gear)
3. Remove bearing, gear, high/low gear sliding
sleeve, spacer ring and thrust ring from the
shaft.
NOTE:
Gear wheel can be taken out from the bottom
hole of the transmission body.
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26
Fig. 3-16
1 Input shaft end cover 2 Reverse shaft end
cover
3 Intermediate gear shaft end cover
3.1.9 Removal of three sets of clutch
gear shafts
1. Lay transmission body flat with the big end cap
surface up, disassemble 3 oil inlet end covers
and remove washers. Remove all seal rings on
the three sets of clutch gear shafts.
NOTE:
Safekeep the seal rings.
Fig. 3-17
1 External oil seal sleeve
2. Remove all external oil seal sleeves inside each
cover.
Fig. 3-18
1 End cover 2 Hoisting bolt
3 Bearing cup
3. Firstly use jackscrew to jack up big end cap,
secondly screw two hoisting bolts into the
mounting holes of the end cover, and finally
operate the crane and disassemble the big end
cap to remove 3 bearing cups wherein.
About 15kg.
NOTE:
The hoisting operation shall be done slowly.
BS428 Transmission Service Manual
27
Fig. 3-19
1 Input shaft assembly
4. Take out input shaft assembly vertically.
NOTE:
Tap lightly on the rear end when it is hard to
take the shaft out.
Fig. 3-20
1 Reverse shaft assembly
2 Countershaft assembly
5. Take out countershaft assembly and reverse
shaft assembly in turn.
Fig. 3-21
1 Stop plate 2 bolt
3 Adjusting screw
6. Erect transmission body, disassemble hexagon
bolts and stop plates on 3 small end covers at
the front and unscrew adjusting screws.
BS428 Transmission Service Manual
28
Fig. 3-22
1 Bolt 2 End cover
3 Adjusting ring 4 Paper washer
7. Disassemble fixing bolts of the end cover to
remove the end cover.
8. Remove 3 paper washers, 2 adjusting rings,
one oil seal (input shaft) and 3 bearing cups
separately.
3.2 Removal of assembly
3.2.1 Removal of transmission control
valve
Fig. 3-23
1 Plug
1. Unscrew the plug and shim from valve stem
locating lock pin and take out spring and steel
ball.
BS428 Transmission Service Manual
29
Fig. 3-24
1 Snap ring
2. Disassemble snap rings at the front and rear of
the valve stem, push forward valve stem, and
squeeze out 2 oil seals and adjusting washers at
the front of the valve holes.
Fig. 3-25
1 Oil seal 2 Adjusting washer
3 Valve stem
3. Then push backward the valve stem, squeeze
out 2 oil seals and adjusting washers at the rear
end of the valve hole and take out the valve
stem.
Fig. 3-26
1 Screw plug
4. Disassemble the screw plug at the front end of
brake valve stem and take out spring seat,
O-ring and spring.
BS428 Transmission Service Manual
30
Fig. 3-27
1 Screw plug 2 O-ring
3 Leather cup 4 Brake sliding valve
5. Disassemble screw plug from the rear end of
valve hole, remove O-ring, and push out brake
valve stem and leather cup.
3.2.2 Removal of three sets of clutch
gear shaft assemblies
NOTE:
● The removal of input shaft assembly shall be
carried out from the front end of shaft to the
rear end. The removal of reverse gear shaft and
countershaft assemblies shall be carried out
from the rear end of shaft to the front end.
● The method of disassembling countershaft and
reverse gear shaft assemblies is similar to that of
input shaft assembly, and the only difference lies
in the direction of clutch. Moreover coMPared
with the input shaft assembly, the countershaft
assembly has one more gear and the reverse gear
shaft assembly one more shaft sleeve. Take input
shaft assembly as example to introduce the
disassembling procedure, and the others will not
be repeated here.
BS428 Transmission Service Manual
31
Fig. 3-28
1 Bolt 2 Stop pad
3 Shaft end baffle
1. Disassemble connecting bolts and stop pad
from shaft end to remove shaft end baffle.
Fig. 3-29
1 Piston ring
2 Internal oil seal sleeve
2. Remove internal oil seal sleeve and 2 piston
rings on it.
Fig. 3-30
1 Shaft sleeve
2 Bearing
3. Remove bearings from both ends of the shaft
and shaft sleeve from the front end of the shaft.
BS428 Transmission Service Manual
32
Fig. 3-31
1 Clutch external drum 2 Bolt
3 Stop pad 4 Gear wheel
4. Remove clutch external drum from the shaft
and disassemble 8 bolts and 4 stop pads as well
as a gear wheel.
Fig. 3-32
1 Emptying valve
5. Disassemble automatic emptying valve (oil
drain valve) base and steel ball on the clutch
housing.
Fig. 3-33
1 Retainer ring
2 External end cover
6. Disassemble retainer ring and take out external
end cover from the clutch. Take out friction
lining: steel disc and wafer.
BS428 Transmission Service Manual
33
Fig. 3-34
1 Special tools 2 Shaft elastic retainer ring
3 Spring 4 Piston
7. Remove retainer ring from housing internal
hub with special tools.
8. Disassemble spring seat, spring and piston.
Fig. 3-35
1 Oil seal ring
9. Disassemble oil seal ring from the piston.
10. Remove O-ring from the housing internal hub.
Fig. 3-36
1 Pinion
11. Press pinion out from the shaft and
disassemble the snap rings at both ends and 2
bearings.
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34
4 Refitting of Transmission
4.1 Refitting of assembly
NOTE:
Wash all parts before refitting.
4.1.1 Refitting of clutch shaft assembly
NOTE:
Three sets of clutch assemblies are of similar structure. Take input shaft assembly as example
to introduce refitting procedure and the others will not be repeated here.
Fig. 4-1
1 Automatic emptying valve
1. Assemble steel ball and automatic emptying
valve (oil drain valve) base.
Fig. 4-2
1 Oil seal ring
2. Assemble O-ring on the housing internal hub.
3. Assemble oil seal ring on piston, apply clean oil
and put the piston into the housing.
NOTE:
● When installing oil seal ring, the sealing surface
shall be placed toward pressure oil surface.
● The oil seal ring is made of rubber and shall be
free of damages caused by crush during assembly.
● The opening width of piston ring shall be within
0.05~0.1mm.
BS428 Transmission Service Manual
35
Fig. 4-3
1 Special tools 2 Retainer ring
3 Spring seat 4 Spring
4. Put lower spring seat, spring and upper spring
seat in the internal hub in turn and use special
tools to compress the spring in order to assemble
retainer ring.
Fig. 4-4
1 Outer friction lining
2 Internal friction lining
5. There are 6 clutch driving plates in all, which are
friction linings made of copper based powder
metallurgy, and 5 driven plates made of steel
with 0.5 mm concavity; make sure to put the
concave surface towards piston end while
refitting.
NOTE:
● The number of outer friction linings for the
three sets of clutches is 6.
● The number of internal friction linings for the
three sets of clutches is 5.
Fig. 4-5
6. Assemble 11 friction linings to the housing in the
sequence of outer gear, inner gear and outer gear
as shown in Fig. 4-5.
NOTE:
● If abrasion that occurs during the usage of outer
friction lining is more than 2/3 in the depth of
pattern groove, replacement is required
immediately.
● Replace the corresponding friction lining only
Outer friction lining
Internal friction lining
BS428 Transmission Service Manual
36
and make sure its number and refitting order is
correct.
Fig. 4-6
1 Retainer ring
2 External end cover
7. Assemble external end cover and snap ring.
Fig. 4-7
1 Bearing
2 Retainer ring
8. Assemble the pinion with snap ring and 2
bearings to the shaft in place.
Fig. 4-8
1 Gear wheel 2 Bolt
3 Stop pad
9. Align gear wheel with the cylindrical pin on the
clutch housing, fasten them with bolts and
meanwhile assemble 4 stop pads to avoid
looseness.
BS428 Transmission Service Manual
37
Fig. 4-9
1 Pinion
10. Lay clutch flat and insert the pinion after
aligning the teeth of internal gear friction linings
with a screwdriver.
Fig. 4-10
1 Shaft sleeve
2 Bearing
11. Turn left and right the pinion continuously until
the spline of the pinion is inserted into the
internal tooth of driven plate, insert input shaft to
ensure the clutch is installed in place and
assemble 2 bearings on both ends of the shaft.
NOTE:
When the length of the extending gear on the
spline shaft is equals to the width of shaft sleeve, it
shows that the clutch is installed in place;
otherwise, it means that the internal teeth of some
driven plates deviate and are not engaged with the
pinion.
Fig. 4-11
1 Piston ring 2 Oil inlet passage
12. Assemble 2 piston rings to internal oil seal
sleeve.
NOTE:
● Piston ring is made of cast iron with greater
brittleness, so it needs to be installed with even
force to avoid damage.
● The openings of two seal rings need to be
staggered, and also have a distance from oil inlet
BS428 Transmission Service Manual
38
3 Internal oil seal sleeve passage.
Fig. 4-12
1 Internal oil seal sleeve
13. Assemble internal oil seal sleeve to shaft.
NOTE:
● Internal oil seal sleeve shall be installed to shaft
by heating evenly in oil at the temperature of
100~150°C.
● Wear heat insulation gloves while refitting, and
the picture is only for reference.
Fig. 4-13
1 Shaft end baffle 2 Stop pad
3 Bolt
14. Install shaft end baffle, stop pad and bolts.
Fig. 4-14
1 Reverse gear shaft assembly
2 Countershaft assembly
4.2 Refitting of assembly components
4.2.1 Assembly of three sets of gear
shafts
1. Lay transmission body flat, put the assembled
reverse gear shaft assembly to the mounting
position in the transmission body and then put in
countershaft assembly.
NOTE:
When refitting, clutch shall be installed by
BS428 Transmission Service Manual
39
rotating.
Fig. 4-15
1 Input shaft assembly
2. Put the assembled input shaft assembly to the
mounting position in the transmission body.
NOTE:
Make sure all sets of gears are correctly engaged.
Fig. 4-16
1 Big end cap
3. Install big end cap to the transmission body, and
fasten the bolts connecting end cover and
transmission body.
About 41.5kg.
NOTE:
Check and replace with new gasket.
Fig. 4-17
1 External oil seal sleeve
4. Install external oil seal sleeves to each cover.
BS428 Transmission Service Manual
40
Fig. 4-18
1 Input shaft end cover 2 Reverse shaft
end cover
3 Countershaft end cover
5. Install three sets of oil inlet end covers, and
fasten the bolts connecting end cover and
transmission body.
NOTE:
● Check and replace with new gasket.
Fig. 4-19
1 1st/reverse gear end cover
2 Neutral gear end cover
● Three oil inlet end covers have the same
appearance but different inside oil passages. The
oil passage of 1st and reverse gears are identical
but different from that of neutral gear.
Fig. 4-20
4.2.2 Refitting of input flange and rear
end cover
1. Install oil seal into input shaft oil seal seat, install
the bearing of input shaft in place by tapping,
and measure and adjust the axial clearance of
input shaft.
Adjusting method:
Use depthometer to measure the depth H from
bearing (cone and cup) to the surface of the
transmission body as well as the height h of oil
seal seat step; select and add adjusting shim
BS428 Transmission Service Manual
41
(δ=0.1mm) to ensure H-h-δ=0.1~0.15mm.
Fig. 4-21
1 Round nut washer 2 Washer
3 Round nut
2. Assemble input flange as well as washer, round
nut and washer in turn and fasten round nuts
using special tools.
Fig. 4-22
1 Adjusting screw
2 Adjusting ring
4.2.3 Assembly of countershaft and
reverse gear shaft rear end cover
1. Install bearing mounting paper washer, bearing
cup and adjusting ring to the rear ends of reverse
gear shaft and countershaft. Install the rear end
covers of reverse hear shaft and countershaft and
fasten them with bolts. Tap adjusting ring in
place through the hole on the rear end cover.
Fig. 4-23
1 Stop pad
2. Adjust the clearance of taper roller bearing
supporting at both ends of the shaft through
rotating the screw in the center of rear end cover.
Install stop pad to fasten the adjusting screw.
Adjusting methods:
Turn the adjusting screw to the limit and then
return by about 15° (the screw pitch is 1mm and
the clearance required shall be 0.25~0.5mm).
BS428 Transmission Service Manual
42
3. Input flange shall be rotated freely.
Fig. 4-24
1 Output shaft assembly
2 Low-speed gear
4.2.4 Assembly of output shaft
1. Assemble bearing, gear, high/low gear sliding
sleeve, spacer ring and thrust ring of the output
shaft, and put them into transmission body.
NOTE:
Low-speed gear can be put into transmission body
from its bottom hole.
Fig. 4-25
1 Bolt 2 Output rear end cover
3 Pressure plate 4 Bolt
2. Tighten the bolts connecting output rear end
cover and transmission body and install 2 oil
seals and dust covers.
3. Install O-ring, pressure plate and fixing bolts that
used to fix rear output flange, and fit lock plate.
Fig. 4-26
1 Iron wire
2 Fixing bolt
4.2.5 Assembly of high/low gearshift
fork mechanism
1. Insert fork shaft, install fork, put fork shaft in the
neutral position, set sliding sleeve to the spline
tooth in the middle of output shaft, align fork
shaft with the thread hole on the fork, then fasten
screws and tighten with iron wire.
NOTE:
The high/low speed lever includes high, neutral
BS428 Transmission Service Manual
43
and low gears, and the travel between two
adjacent positions is 15mm.
Fig. 4-27
1 High/low gearshift fork 2 Screw plug
3 Steel ball 4 Spring
5 Oil seal
2. Install spring and steel ball, fasten screw plug
and washer and install gearshift shaft oil seal.
Fig. 4-28
1 Bolt
4.2.6 Assembly of oil sump
1. Install gasket and fasten the bolts connecting oil
sump and transmission body.
NOTE:
● Check and replace gasket.
● The bolts shall be fastened diagonally in several
steps.
Fig. 4-29
1 Bolt
4.2.7 Assembly of transmission control
valve
1. Install upper paper washer, bottom plate and
lower paper washer to transmission control
valve.
2. Erect transmission body and install transmission
control valve to the transmission body.
NOTE:
The bolts shall be fastened diagonally in several
BS428 Transmission Service Manual
44
steps.
Fig. 4-30
1 Cover plate
2 Breather
4.2.8 Assembly of breather and cover
plate
1. Install cover plate and paper washer, fasten the
bolts on them and screw on the breather.
NOTE:
The bolts shall be fastened diagonally in several
steps.
Fig. 4-31
1 Oil seal cover 2 Oil seal
3 Output shaft flange 4 Dust cover
5 Brake caliper disc
4.2.9 Assembly of parking brake
assembly
1. Install oil seal cover to transmission body.
Fig. 4-32
1 Pressure plate
2 O-ring
2. Install O-ring and pressure plate.
BS428 Transmission Service Manual
45
Fig. 4-33
1 Lock plate
2 Bolt
3. Screw up the fixing bolts on the output flange
and assemble upper lock plate.
Fig. 4-34
4. Install parking brake and fasten connecting bolts.
Fig. 4-35
1 Filter
2 Oil filler pipe
4.2.10 Assembly of oil filler pipe and
filter
1. Install filter with O-ring and fix them to
transmission body.
2. Install oil filler pipe and O-ring, and fasten
connecting bolts.
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46
5 Service Tools for Transmission
Table 5-1
Special tools Tool name Location to be used Remarks
Transmission mounting
bracket
To support and tilt
transmission
If not available, a
disassembly and assembly
platform can be set up.
Hoisting tools End cover M10
Socket Round nut on the
input shaft
Disassembly and
assembly tool of clutch
spring
Three sets of clutch
springs
Depth meter Input shaft Spec: 0.02/0~200
Transmission pressure
joint
Pressure joint of
relief valve 6410006223
Pressure testing hose
Use with pressure
joint and pressure
gauge.
4030000368
Pressure gauge with a
gauge of 25 bar 6430000943
BS428 Transmission Service Manual
47
6 Common Fault Diagnosis and Troubleshooting
Table 6-1
Symptoms Probable causes Solution
1. Weak traveling and gear
shift seizure
Low oil level, and empty pump Check if the oil level is below
oil dipstick and add oil
Oil suction filter element falls
off or is blocked up
Check, wash and replace after
removal
The inner layer of oil suction
pipe is peeling off
Check and replace after
removal
Air enters oil suction pipe Check
Relief valve is adjusted to a too
low pressure
Check, adjust and replace valve
Pump abrasion and oil leakage Replace pump
The oil drain pipe of torque
converter is blocked up
Check, wash and replace
The opening pressure of
overflow valve is too low
Raise the opening pressure
Transmission clutch slipping Check transmission after
removal
Piston oil seal ring has abrasion
or damage
Replace
Oil passage from relief valve to
pilot valve is blocked up
Check pipeline
Transmission shaft end ring or
sleeve shows abrasion
Replace seal ring and sleeve
2. High oil temperature Low oil level, and empty pump Check oil level and add oil
BS428 Transmission Service Manual
48
Symptoms Probable causes Solution
Oil suction filter element falls
off or is blocked up
Check, wash and replace after
removal
The inner layer of oil suction
pipe is peeling off
Check and replace after
removal
Air enters oil suction pipe Check
Pump abrasion and oil leakage Replace pump
Low transmission pressure and
clutch slipping
Raise pressure or find out
causes
Torque converter has large
inside leakage
Check torque converter after
removal
Oil temperature gauge and
sensing plug are broken
Replace
3. Low oil pressure
Low oil level, and empty pump Check oil level and add oil
Oil suction filter element falls
off or is blocked up
Check, wash and replace
Air enters oil suction pipe or its
inner layer is peeling
Check and replace
Transmission shaft ring or
sleeve shows abrasion
Replace seal ring and sleeve
Piston oil seal ring has abrasion
or damage
Replace
The spring of relief valve is
broken
Check and replace valve
Pump abrasion and oil leakage Replace pump
Pressure valve is adjusted to a
too low pressure
Adjust again
Oil passage from relief valve to Check pipeline
BS428 Transmission Service Manual
49
Symptoms Probable causes Solution
pilot valve is blocked up
4. Abnormal sound
Propeller shaft is installed in a
wrong direction
Follow the direction of arrow
Vortex appears when opening
relief valve
Replace relief valve
Internal parts are damaged or
gears have poor accuracy
Check after removal
5. High/low gear is out of
mesh
The positioning steel ball of
fork is abraded flat causing the
ball unable to work normally
Check and replace
Steel ball shows serious
abrasion
Check and replace
Spring is damaged Check and replace
The depth of positioning hole
for locking screw is insufficient
causing the fork cannot be
locked by screw securely
Check and replace
Locking screw is sliding, etc. Check and replace
6. Only one gear is normal
and others have low
pressure
Oil inlet end cover is installed
in a wrong way
Exchange
The oil seal ring or piston ring
of other two gears are damaged
Check and replace
7. Only one gear is
available, and the vehicle
can run even in the neutral
gear
The clutch of one gear is burnt
out and friction lining is unable
to separate
Check and repair
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50