I–Shift Generation C Design and Function

Service BulletinVolvo Truck CorporationGteborg, Sweden Trucks

Date Group No. Release Page

12.2010 431 228 10 1(31)

IShift generation C

Design and function

FH, FM, FH16

AT2412C, AT2512C, AT2812C,ATO2512C, ATO3112C

IShift generation C, design and function

T4021207

The service information describes the design and function of AT gearboxes.

88983778ENG43273 English

Printed in Sweden

Volvo Truck Corporation Date Group No. Release PageService Bulletin 12.2010 431 228 10 2(31)

Gearbox, mechanicalI-Shift, Generation C

Contents General, page 3 Gear ratio, page 4 Gearbox construction, page 4 Synchronisation, page 6 Range housing, page 6 Range gear, page 6 Emergency steering servo pump, page 7 Oil cooler, page 7 Control housing, page 8 Countershaft brake, page 10 Clutch cylinder, page 11 Lubrication system, page 11 Ventilation, page 14 Electrical system, page 15 Compressed air system, page 17 Power train, page 18 Auxiliary brake lever, page 24 Gear selector, page 25 Display, page 25 Program packages, page 26 Function description, page 28 Communication with other control units, page 29


General

T4021207

Make VOLVO

Type

AT2412CAT2512CAT2812CATO2512CATO3112C

Unsynchronized main gearbox

Symbols ATO2512C

A - AutomaticT - TransmissionO - Overdrive25 - Torque 2500 Nm12 - Number of forward gearsC - Generation

Range gear Synchronised

Split gear Synchronised

Forwards 12Number of gears

Reverse 4

AT2412C, AT2512C, ATO2512C AT2812C, ATO3112C

Weight without oil 271 kg 277 kg

Length 891 mm 909 mm


Gear ratioGear engaged AT2412C, AT2512C, AT2812C ATO2512C, ATO3112C

1st 14,94:1 11,73:1

2nd 11,73:1 9,21:1

3rd 9,04:1 7,09:1

4th 7,09:1 5,57:1

5th 5,54:1 4,35:1

6th 4,35:1 3,41:1

7th 3,44:1 2,70:1

8th 2,70:1 2,12:1

9th 2,08:1 1,63:1

10th 1,63:1 1,28:1

11th 1,27:1 1,00:1

12th 1,00:1 0,79:1

Reverse gear (R1) 17,48:1 13,73:1

Reverse gear (R2) 13,73:1 10,78:1

Reverse gear (R3) 4,02:1 3,16:1

Reverse gear (R4) 3,16:1 2,48:1

Gearbox constructionThe gearbox construction consists of three main parts:a clutch housing, a basic housing and a range housing.The clutch housing forms the front end plate of thegearbox. The base housing contains the main, counter

and reverse shafts along with a selector unit which isintegrated into the control housing. The range housingcontains the range gear planetary gear and the outputshaft.

T4021405

1 Clutch housing

2 Main housing

3 Range housing for the retarder


The main parts in the gearbox are the input shaft, mainshaft, range gear with selector unit, countershaft, oilpump with reverse shaft, as well as the control housingwith selector unit.

The trailing wheels for the reverse gear and basic gearsare located on the main shaft. The range gears sun gearis also integrated with the main shaft. The countershafthas fixed gears.

The range gear incorporates a planetary gear and isintegrated with the output shaft.

Gearboxes equipped with a power take-off also have adrive shaft fitted.

T4021728

1 Input shaft

2 Main shaft

3 Range gear with selector unit and retarder drive

4 Countershaft

5 Oil pump with reverse shaft

6 Control housing with selector unit

7 Drive shaft for power take-off


Synchronisation Split gear (A) is synchronized. The main gearbox housing (B) with its gears is not

synchronized.

Range gear (C) is synchronized.

T4021404

Range housingRange housing (C) can be combined with:

Power take-off; see option instructions for variants Emergency steering servo pump Retarder unit

Range gearThe range synchronization lies outside the ring gear,reducing the units length. The large synchronization arearesults in short selection time, the wide planet gears give

a strong range and the helical gears result in a quietplanet gear.

T4021725

Range gear with selector unit and retarder drive


Emergency steering servo pumpThe emergency steering servo pump is located on thegearbox and is driven by the gearbox output shaft. Theemergency steering servo pump is activated when forsome reason the normal power steering circuit fails.

T4021683

Emergency steering servo pump, PSS-DUAL

Oil cooler

T4021755

The gearbox oil cooler function is not affected by whether the gearbox has a retarder or not.


Control housingGears are selected using the gear selector. Once a gearhas been selected, the system reduces the engine torqueto a suitable level, after which the gears are shifted toneutral.

After the gearbox has been put into neutral, the enginespeed is adjusted to accommodate the speed of theselected gear, after which the gear shift takes place.

The control housing cover has two or sometimesthree electrical sockets.

When there is no retarder, the following applies:

I Vehicle communication

II Clutch cylinder

III

The following applies with retarder:

I Vehicle communication

II Retarder

III Clutch cylinder

T4018492

The control housing incorporates nine solenoidvalves:

2. Solenoid valve 2nd gear

LR. Solenoid valve, low range

3. Solenoid valve 3rd gear

HR. Solenoid valve, high range

B. Solenoid valve, brake

HS. Solenoid valve, high split1

R. Solenoid valve, reverse

LS. Solenoid valve, low split1

1. Solenoid valve 1st gear

1 HS and LS have reversed functions on Over Drive gearboxes.

T4018189


The control housing incorporates the followingcomponents:

Four parallel cylinders, split, 1/R and 2/3 and range. Four inductive sensors for the positioning of the

pistons.

Two speed sensors, one for the main shaft and onefor the countershaft. The input shaft speed is set bythe countershaft sensor.

An oil temperature sensor, selector forks for splitgears and main gearbox. The oil temperature sensoris located on the cabling for the rpm sensor.

A pressure sensor. Control unit for transmission, TECU.

T4018494

Locations of cylinders and position sensor

A. Split cylinder

B. 1/R cylinder

C. 2/3 cylinder

D. Range cylinder

E. Position sensor for the split cylinder

T4018201

Location of position sensor and speed sensor

A. Position sensor range cylinder

B. Speed sensor, countershaft

C. Speed sensor, main shaft

D. Position sensor, 2nd and 3rd cylinders

E. Position sensor 1st and reverse cylinder


Parameter settings for installation of GCU-D(GCU-D: Gear Control Unit for I-Shift generation D)

For more information regarding GCU-D and theseparameters, see Function Group 4319, Information typeDiagnostics MID 130 PID 160 Parametersetting.

T4057801

GCU

ID Unit Designation

0 The main shaft has a 72 teeth sensor wheel mountedKBQ

1 The main shaft has a 30 teeth sensor wheel mounted

0 There is a speed-sensor-D1 mounted

KBR1 There is a speed-sensor-C2 mounted

1 Speed sensor for I-shift gearbox generation D

2 Speed sensor for I-shift gearbox generation C

Countershaft brakeThe counter shaft brake is located at the front of thecounter shaft and brakes the rotating parts the gearboxwhen a start gear is selected, which eliminates gearboxwear, deposits and noise. The brake is also sometimesused during changing up to give quicker gear changes. Itis activated using an integrated pneumatic cylinder.

T4021408

Countershaft brake


Clutch cylinderThe clutch cylinder is located in the clutch housing,concentrically round the input shaft with a position sensorwhich measures clutch wear. A valve unit controls theclutch cylinder and is located on the outside of the clutchhousing.

T4021655

A. Clutch cylinder

B. Position sensor

C. Valve unit

D Bleeder nipple for the valve unit.

Lubrication system

T4023570


The gearbox is lubricated through a combination ofpressure and splashing.

The oil is led into the main shaft to lubricate and cool therange gears as well as the input and main shaft bearings.

The countershaft brake, output shaft bearings, emergencysteering servo pump drive, retarder gear and powertake-off are also lubricated.

The lubrication system has two overflow valves. Onevalve ensures that the gearbox is lubricated if thefilter gets blocked while the other prevents excessivepressures in the system, e.g. during cold start. The valvesare made up of a compression spring and a valve peg. T4021730

The overflow valve which ensures that the gearbox is

lubricated.

T4021729

Overflow valve which prevents excessive pressure.

Oil pumpThe oil pump is an eccentric pump driven by thecountershaft via a gear. The pump is mounted in twoneedle bearings in the reverse shaft.

There is a full flow oil filter of the insert filter type on thepressure side of the pump. It is located in the oil filterhousing in the main housing. A support pipe is fittedin a cover that is fastened to the bottom of the oil filterhousing. The support pipe prevents the filter, which sitson the outside, from collapsing.

T4021520


Oil levelThe oil level is checked with a level glass (2) and adjustedusing two drain plugs (1A and 1B) and two filler plugs(3 and 4).

Over-filled oil can also be adjusted using level plug (3).

Read more about oil quality and oil change volumesinFunction Group 1750, Information type Service andmaintenance Preventive maintenance intervals.

T4021684

Level glass for checking oil level

T4033600

1A. Drain plug

1B. Drain plug

2. Level glass

3. Filler plug/level plug

4. Filler plug / Vent valve


VentilationVentilation is via a hose that passes over the controlhousing and down behind the valve unit.

T4021686


Electrical systemSensors and sockets, for gearboxes without a retarder

T4021412

I. Vehicle communication

II. Clutch cylinder

A. Speed sensor

T4021413

Cabling from socket I to the speed sensor andchassis cabling.

T4021414

Cabling from socket II to the valve unit for theclutch cylinder.


Sensors and sockets, for gearboxes with a retarder

T4021409

I. Vehicle communication

II. Retarder

III. Clutch cylinder

A. Speed sensor

T4021411

Cabling from socket I to the speed sensor andchassis cabling.

T4021410

Cabling from socket II to the retarder.

T4021418

Cabling from socket III to the valve unit for theclutch cylinder.


Compressed air systemCompressed air connections

T4021415

Compressed air connection between the control housing

and the valve unit for the clutch cylinder.

T4021416

For the high pressure system, compressed air connection

between the control housing and the four-circuit valve.

For the low pressure system, compressed air connection

between the control housing and the pneumatic tank.

T4021417

Pneumatic connection between the control housing and the

countershaft brake.


Power trainThe following illustrations show the power train forAT2412C, AT2512C and AT2812C.

T4021693

1st gear

T4021694

2nd gear

T4021695

3rd gear

T4021696

4th gear

T4021697

5th gear

T4021698

6th gear


T4021699

7th gear

T4021700

8th gear

T4021701

9th gear

T4021702

10th gear

T4021703

11th gear

T4021704

12th gear


T4021691

Neutral N1

T4021692

Neutral N2

T4021687

Reverse gear (R1)

T4021688

Reverse gear (R2)

T4021689

Reverse gear (R3)

T4021690

Reverse gear (R4)


The following illustrations show the power train forATO2512C and ATO3112C.

T4021711

1st gear

T4021712

2nd gear

T4021713

3rd gear

T4021714

4th gear

T4021716

5th gear

T4021715

6th gear


T4021717

7th gear

T4021718

8th gear

T4021719

9th gear

T4021720

10th gear

T4021721

11th gear

T4021722

12th gear


T4021709

Neutral N1

T4021710

Neutral N2

T4021705

Reverse gear (R1)

T4021706

Reverse gear (R2)

T4021707

Reverse gear (R3)

T4021708

Reverse gear (R4)


Auxiliary brake leverOn all vehicles with a retarder and on vehicles with anautomatic gearbox and engine brake (VEB) the auxiliarybrake is applied using a lever on the steering shaft.

0 Auxiliary brake not applied

A Automatic mode

13 Manual mode

B Position for activating the brake program. Spring returnto position 3.

T5012243

The illustration shows a vehicle fitted with the Basicprogram set, which has no brake program. When theauxiliary brake lever is moved to position B, the gearboxwill select a gear giving an engine speed of just over 1500rpm. If the speed in reduced, the gearbox will then selectgears to maintain an engine speed between 1000-1500rpm (B). The driver can also change down further bymoving the auxiliary brake lever to position B.

T4022470

Without the brake program, (A) desired rpm for first change

down, (B) area for braking using the auxiliary brake.

The vehicle in the illustration is fitted with one of theprogram sets Distribution & Construction, Long HaulFuel & Economy or Heavy Duty GCM Control, whichinclude the braking program. When the auxiliary brakelever is moved to position B, the gearbox will select a geargiving an engine speed above 1500 rpm. The gearboxwill then select gears to maintain an engine speed above1500 rpm (B).

T4022471

With the brake program, (B) area for braking using the

auxiliary brake.

Note: The effect of the auxiliary brake may be reducedby the I-shift control unit, MID 130, to make the ride ascomfortable as possible. The effect reduction is regulatedby the selected gear, vehicle weight and road surfaceinclination.

For more information on auxiliary brake component parts,see group 21, Description, Design and Function, Engine.


Gear selectorGear selector (GLU) is attached to the drivers seat andcan be folded away to ease passage inside the cab. Thegear selector control unit is in the dashboard.

The gear selector incorporates the following functions:

1 Three position switch with spring return for up anddown changing.

2 Button for lowering the lever into a horizontal position.

3 Gear selector inhibitor preventing the vehicle frombeing put in gear unintentionally.

4 Gear selector position:R = reverse gearN = neutralA = automaticM = manual

5 Button E/P for economy/performance position.

6 Button L Limp Home.

Note: The Limp Home function is intended for movingthe vehicle short distances in order to get off the roadand to a workshop. Only one gear can be used and thedriving may be jerky. For information on how to engageand use this function, see driver instructions.

T4022483

DisplayThe display provides information on the gear currentlyselected and which gears are available.The display is divided into smaller fields showing:

1 Driving program

2 Selected gear

3 Available gears (down/up)

4 Lever position

T3014422


Program packagesGeneral notes on the program packagesThe gearbox has different functions depending on whichprogram package is installed in the gearbox.The following program packages are available:

Basic is the standard gearbox program Distribution & Construction include functions that

make the truck lighter to manoeuvre.

Long Haul Fuel & Economy include functions thatpartly improve fuel consumption and partly make thetruck lighter to manoeuvre.

Heavy Duty GCM Control is designed for heavytrucks. This program also contains functions that helpto improve fuel consumption and make the truck easierto manoeuvre.

Which program package is installed in the vehicle?When the gear selector is in neutral position (N) and theFOLD button is pressed in, the lever can be foldedforwards. The display then shows the program variantthe gearbox has.

Display Programpackages

VDA variants

B Basic TP-BAS

DC Distribution &Construction

TP-DICON

FE Long Haul Fuel& Economy

TP-FUEC

HD Heavy DutyGCM Control

TP-HD

Change program package

When a program package is replaced, the Central system(VDA) must be updated before it can be downloadedto the vehicle. This is done by entering the Convertingset number in the computer tool which is stated in Partinformation, accessory.

After replacement, reprogramming must be carried outusing the TECU control unit (MID 130), and the gearboxmust be recalibrated.

Functions in every program package

Function BasicDistribution &Construction

Long Haul Fuel &Economy

Heavy Duty GCMControl

I-Roll X X

Smart Cruise Control X X

Launch Control X X X

Enhanced Shift Strategy (GCM 60 T)

X X X

Heavy Duty GCM Control (60 T< GCM 180 T)

X

Possible optional functionsBasic

Distribution &Construction

Long Haul Fuel &Economy

Heavy Duty GCMControl

Gear Selection Adjustment inAuto including Kickdown

X X X

Enhanced Power Take OffFunctions

X X X X

Variant for optional functionsName Variant Installed Not installed

AMSO-AUT XGear Selection Adjustment in Auto

AMSO-BAS X

APF-ENH XEnhanced Power Take Off Functions

APF-BAS X

Customer parametersCustomer parameters in the gearbox control unit: Note: The default value can vary depending on the

program package selected.


ID Designation Default Value Unit

FZC Highest used start gear (1 6). 6

GJJ Load on the engine PTO even when it is deactivated.1 No Yes/No

GJIDetermines whether the transmission is disconnected from theclutch in Auto Neutral.1 2

No Yes/No

GJGDetermines how the split gear performs when PTO 1 isconnected for the gearbox.1

Selectable LS/HS/Selectable

GJHDetermines how the split gear performs when PTO 2 isconnected for the gearbox.1

Selectable LS/HS/Selectable

IEO

Determines how the transmission performance mode is handled:Manual: Performance mode available.Auto: Performance mode available. The transmission willautomatically return to Economy mode when the engine is nolonger operating under high load.Disable: Performance mode not available.

Auto Manual/Auto/Disabled

1 For further information, see options instructions.

2 GJI only used at APF-ENH; the others are always included.


Function description

Standard functionsThe following standard functions are available in thegearbox:

Automatic choice of start gear. Possibility to change automatically selected gears

when the accelerator pedal is released.

A display that shows the gearbox oil temperature anda warning system that informs the driver when the oiltemperature is too high.

Optional functions I-Roll (VEB or retarder required)

This function automatically engages and disengagesthe freewheel to reduce fuel consumption. Whenyou release the accelerator, the transmission shiftsto neutral, so that the vehicle can roll freely and theengine goes down to idle.

Smart Cruise ControlThe function is only active when cruise control isactivated. Saves fuel by deactivating the auxiliarybrakes under certain conditions. The function releasesthe auxiliary brakes after a downhill stretch, whichimproves cruise control performance.

Launch ControlAllows driving with the engine idling without slippingthe clutch.

Regulates engine torque when pulling away foroptimum gear changing and avoid high engine speed.

The following functions in Launch control requireEBS:

Improved comfort when pulling-up through smootherdisengagement when pressing lightly on the brakepedal.

Automatic application of the brakes when the vehiclerolls in the wrong direction, in relation to the selectedgear.

Automatic application of the brakes to stop the vehicleand change from a forward to a reverse gear or viceversa.

HSA, Hill Start Aid, which is only active on inclines.See also the description of Hill Start Aid: Functiongroup 593, Information type Description Electronicallycontrolled braking system (EBS).

Enhanced Shift Strategy

Automatically selects the lowest possible gear whenthe air suspension is in manual mode in order to obtainoptimal manoeuvrability. ECS required.

Improves engine brake performance by selecting gearsthat increase engine speed.

Temporarily applies the wheel brakes when changinggear to compensate for the engine brake whenthe brake program is active. This function requiresABS-EBS. If a trailer without ABS is hitched up, thefunction is deactivated.

Heavy Duty GCM ControlThis function makes it possible to adjust the gearingstrategy to suit the rolling weight - up to 180 tonne.

Gear Selection Adjustment in Auto includingKickdownThe function makes it possible to adjust automaticallyselected gears even when the accelerator pedal isdepressed. There is also a Kick Down function formaximising the acceleration of the vehicle.

Enhanced Power Take Off FunctionsOptional functions that support power take-offoperations, e.g. Auto Neutral and splitbox. Optionalfunctions:

Makes it possible to determine software parametersthat limit engine speed when power take-off is used.The function forms a gear selection strategy to suitengine speed limitations.

Disengages the transmission at the request of theoptions module, irrespective of the gear lever position,when Auto Neutral is activated.

Blocks reverse gear when the options module requests reverse inhibit.

Makes it possible to use the splitbox for driving thepower take-off at high capacity.


Communication with other control units

Summary, components (signal summary)

T4058439

Component list

Component Description

A03 (MID 140) Central instruments

A12 (MID 136) Control unit, ABS

A13 (MID 130) Control unit, TECU (transmission electronic control unit)

A14 (MID 128) Control unit, EECU (engine electronic control unit)

A16 (MID 150) Control unit, ECS (electronically controlled suspension)

A17 (MID 144) Control unit, VECU (vehicle electronic control unit)

A21 (MID 136) Control unit, EBS (electronically-controlled brake system)

A27 (MID 216) Control unit, LCM (external lighting)

A33 (MID 220) Tachograph

A36 (MID 249) Control unit, BBM (body builder module)

A41 (MID 222) Control unit, RECU (retarder control unit)

A109 (MID 223) Control unit, GSECU (gear selection electronic control unit)

B04 Sensor, engine speed, crankshaft

B12 Sensor, tachograph/speedometer


B13-73 Sensor, wheel speed

B25 Sensor, accelerator pedal

B55-58 Sensor, air pressure in air spring bellows

B175 Sensor, load indicator

S07 Switch, engine brake

S08/S09 Switch, differential lock

S24 Retarder stalk switch

S25 Switch, cruise control

S28 Power take-off switch

S59 Position switch, brake pedal, NO

S171 Gear lever, GLU

XO5 Trailer connector, 7-pin, 24 S

Y39 Solenoid valve, VEB (Volvo engine brake)

Communication with control unit VECU (A17), MID 144Signals / information to TECU:

The vehicle control unit parameters MG, MH and AQmust have the same values. Check the parametersettings in the VDA.

Accelerator pedal position, including kick-down. Cruise control. Retarder control. For further fault tracing see the

PC-tool, function group 5.

Power take-off control, see options instructions. Brake pedal position. Parking brake applied or not. The VECU K-factor must be the same as the

tachograph K-factor.

Vehicle weight information on leaf suspension vehicles( RADD-BR and RADD-TR), used for gear selection.

Communication with the control unit Central instruments (A03), MID 140Signals / information from TECU:

Gear selector, positions. Gear selected. Possible gears. Driving program E/P. Time and date for diagnostics.

When using the power take-off, the driver can choosebetween N1=low split and N2=high split for differentPTO gear ratios, see the options instructions.

When the gear lever is in neutral position (N) and thebutton FOLD is pressed in, the lever can be foldedforwards, and the display shows which program setthe gearbox has.

Communication with control unit EECU (A14), MID 128Signals / information to TECU:

Engine speed. Engine configuration

Engine torque If the engine is not running smoothly, this will adversely

affect gear shifting.

Communication with control unit ABS/EBS (A12/A21), MID 136Signals / information to TECU:

Wheel speed sensor. Wheel spin information; the vehicle does not change

gear.

ABS system active, the vehicle does not change gear. Information from ESP, the vehicle does not change

gear.

If Traction Control is disengaged via the display, thegearbox may change gear due to spinning.

In Launch Control the gearbox can control thebrakes. For more detailed information, see Functiondescription, page 28 for Launch Control.

Communication with control unit ECS (A16), MID 150Signals / information to TECU:

Vehicle weight. ECS control unit status. Always start in 1st gear if

the manoeuvre control unit for the air suspension is inmanual mode.


Communication with control unit LCM (A27), MID 216Signals / information to TECU:

Trailer coupled. The gearbox can select the wrong start gear and

wrong gears if the parameter ANI is not active. Thegearbox then assumes that a trailer is hitched up.

Communication with control unit BBM, MID 249Signals / information to TECU:

Power take-off (PTO) engagement. Power take-off switch control.

I–Shift Generation C Design and Function

Documents

range gear planetary

gear selector

gear ratiogear

reverse gear r1

reverse gear r2

reverse gear r3

reverse gear r4

range gears