Not Just Another CVT N˜t - Transmission Repair and ... · Not Just Another CVT A ... • line pressure • transmission oil temperature ... circuits for a return signal. The position

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Apair of new transmissions were introduced in the 2014 Chevrolet Spark (C Body):

The CVT-7 and 1ET35. We’ll take a look at the details of each of them.

The CVT-7 (RPO M4M) is manu-factured by Jatco Corporation (known as a model APO by Jatco) and it’s also used in some Nissan models (JF015E). Unlike most other CVTs on the market, the CVT-7 is a two-step unit, designed to provide improvements in fuel econo-my and performance when compared to a conventional CVT.

The gear ratio of the CVT is expanded with an auxiliary gearbox, which is a planetary gearset attached to the output pulley. The two forward gear ratios are 1.821:1 and 1.000:1 and the

reverse gear ratio is 1.714:1.The two-step gear ratio is con-

trolled by the addition of the auxiliary portion of the transmission. This allows for using smaller pulleys, reducing the overall length by 10% and the weight by 13%. The new pulley size allows the pulleys and belt to be repositioned in the case, reducing friction loss by 30% because the oil isn’t being agitated as much.

A dedicated transmission controller sits under the driver’s side of the dash, near the brake pedal. Like other TCMs, it must be programmed if replaced.

The inputs to the controller are carried on the CAN data bus (engine

RPM, torque, load, ABS, etc.) Sensors include:

• engine• primary, secondary, and output

speeds• line pressure• transmission oil temperature

…and an inhibitor switch. Outputs include pressure control and engine torque request via CAN.

Fluid Level and Type The transmission has a stand pipe

for checking fluid level; there’s no dip-stick even though it has a dipstick tube. The dipstick tube provides a fill point for the transmission.

Check the fluid level at 122ºF (50ºC) with the engine running, in park,

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on level ground. Remove the stand pipe plug and look for ATF to drip from the stand pipe:

• If nothing comes out, you’ll need to add fluid.

• If fluid rushes out, the unit is overfilled: Allow the excess fluid to drain.

• When the fluid level is cor-rect the fluid should drip from the stand pipe.

The fluid is CVTF I Green Fluid, GM part number 19260800. Fluid capacity is 6.21 qts (5.88L).

Line PressureThis unit doesn’t have a

pressure tap. The only way to check line pressure is with a scan tool. Normal line pressure: 1.2L engine 72.5 PSI at idle; 652-725 PSI at stall. 1.0L engine 72.5 PSI at idle; 620-693 PSI at stall.

PulleysEach pulley consists of one

fixed sheave and one moveable sheave. The pressure applied to the primary and secondary pulley pistons determines the ratio and torque capacity by vary-ing the size of the two pulleys. Pulley size and the ratio available from the auxiliary gear box planetary system determine the over-operational 7.3 ratio spread (figure 1).

Clutches and BrakesOne drive clutch and two brake

clutches are used. The low brake and high clutch apply in D and M ranges and are controlled based on the gear ratio required. The reverse brake only applies in reverse.

Oil Pump The CVT-7 uses an off-axis, chain-

driven, vane-style pump.

Auxiliary Gear BoxThe gear box consists of a plan-

etary gearset, and the high, low, and reverse clutches/brakes.

Figure 2

Figure 1

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Reduction Gearset (Counter Gears)

Like other transmissions, the reduc-tion gearset transmits power from the transmission section to the final drive. The counter gear ratio varies depending on the engine. The 1.0L engine uses a 1.178:1 ratio while the 1.2L engine uses a 0.967:1 ratio. Both applications use a 3.882:1 final drive ratio.

Valve Body, Solenoids, Sensors, and Valves

The valves, solenoids, and sensors used by the CVT-7 include (figure 2 and 3):

• Control Valve: Controls oil pres-sure from the pump to feed the rest of the valve body and control systems

• Pressure Regulator: Controls line pressure

• Torque Converter Regulator: Controls the pressure within the torque converter

• Torque Converter Clutch Control Valve: Controls the pressure to the TCC solenoid

• Pilot Valve: Controls pressure feeding each solenoid

• High Clutch/Reverse Brake Switching Valve: Controls when pressure goes to the high clutch or reverse brake

• Manual Valve: Determines gear range based on shifter position

• Primary Pressure Control Valve: Controls pressure to the primary pulley to control primary pulley operation

• Primary Solenoid: Controls the primary pressure control valve (N/H solenoid)

• Low Brake Solenoid: Controls the operation of the Low Brake (N/L solenoid)

• High Clutch and Reverse Brake Solenoid: Controls the operation of the high clutch and reverse brake. (N/H solenoid)

• TCC Solenoid: Controls the TCC control valve (N/L solenoid)

• Line Pressure Solenoid: Controls the pressure regulator valve (N/H solenoid)

• Fluid Temp Sensor: A thermis-tor that creates a signal based on transmission fluid temperature

• Secondary Pressure Sensor: A variable pressure sensor that cre-ates a signal based on the pressure applied to the secondary pulley piston

• High Clutch Oil Pressure Switch: Signals whether oil pressure is being fed to the high clutch

ROMThe CVT-7 uses a ROM (Read

Only Memory) box mounted to the valve body area. It stores baseline cali-bration comparative data for the sole-noids and can only be replaced with the valve body assembly.

Figure 4

Figure 3

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Adaptive Learning Reset Like other transmissions, the

CVT-7 uses adaptive learning to improve transmission operation. The reset process synchronizes the trans-mission ROM to the TCM calibration. You’ll need to reset the adaptive learn-ing values during any of these condi-tions:

• TCM was replaced or repro-grammed

• Internal repairs that could affect transmission operation

• Transmission was replacedTo reset the adapts, use a scan tool

and select the “Transmission Adaptive Pressure Reset” function. This process will take about 10 seconds (figure 4).

Another transmission available for the Chevrolet Spark (C Body) is known as the 1ET35 (RPO MME). It’s an elec-tric drive transmission.

The 1ET35 is a fully automat-ic, front wheel drive, variable-speed, electronically-controlled transmission. It consists of one 85kW, 360-volt, 3-phase electric drive motor; one plan-etary/differential gearset; an internal

mode switch (IMS); a temperature sen-sor; a high-voltage electric auxiliary fluid pump; and the housing (figure 5).

The hydraulic system uses an elec-tric auxiliary fluid pump motor assem-bly located inside the transmission for cooling and lubricating rotating compo-nents. This system consists of a gerotor-type pump; an electric, 3 -phase, 360-volt, high voltage pump motor; a wiring harness; and a control module.

The control module is located under the hood, inside the drive motor generator power inverter module. The transmission fluid pump operates under low pressure and will only run when the transmission is out of park or neutral and the module detects vehicle speed.

The drive motor is a permanent magnet, 85 kW peak-power AC motor, and is controlled by the power inverter module. Drive motor speed is controlled and monitored by a resolver-type posi-tion sensor (like the 2ML70). The drive motor generator power inverter module monitors the angular position, speed, and direction of the drive motor based on the signals from the position sensor

to the drive motor gen-erator power inverter module.

The drive motor position sensor, or resolver, contains a drive coil, two driven coils, and an irregularly shaped metallic rotor.

The metallic rotor is mechanically attached to the shaft of the drive motor generator. When the vehicle is on, the drive motor generator power inverter module out-puts a 5 VAC, 10 kHz excitation signal to the drive coil. The drive coil excitation signal creates a magnetic field surrounding the two driven coils and the irregularly shaped rotor.

The drive motor generator power invert-er module then moni-tors the two driven coil

circuits for a return signal. The position of the irregular shaped metallic rotor causes the magnetically-induced return signals of the driven coils to vary in size and shape. A comparison of the two driven coils’ signals allows the motor control module to determine the exact angle, speed, and direction of the drive motor.

FluidThe 1ET35 uses Dexron VI HP,

GM part number 19300536. The fluid capacity is 4.4 qts (4.2L).

Lately it seems as though there’s a new transmission being introduced every day. But a careful examination of the details shows that these new trans-mission aren’t all that different than those you’ve already seen. Once you identify the details, the rest isn’t all that difficult to understand… or repair.

Portions of materials contained herein have been reprinted with permission of General Motors Corporation, Service Technology Group Agreement # 061O228.

Figure 5

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