VT40 CVT Transmission Slipping Condition

There may be a slipping condition, a loss of forward gear and/or an illuminated Check Engine light on some 2019-2021 Malibu and 2020-2021 Trailblazer and Encore GX models equipped with the VT40 CVT automatic transmission (RPO MRG). DTC P2714 (Transmission Control Solenoid Valve 4 Stuck Off) also may be set in the Transmission Control Module (TCM).

These intermittent conditions may be caused by the clutch regulator valve sticking in the valve body, damage to the forward clutch piston, and/or wear in the primary pulley bearing bore causing damage to the case.

 

Transmission Fluid Temperature

Before beginning diagnosis, verify the transmission fluid is at the proper level following the procedure in the appropriate Service Information. The transmission fluid temperature must be between 140°-176°F (60°-80°C) to properly check the fluid level and to perform the diagnostic procedures.

 

Test Drive

If the fluid level is correct, with the transmission at operating temperature, drive the vehicle to determine if there is a slip or lack of engagement in Drive. If there is no slip in Drive, clear the DTCs and drive the vehicle again. If the DTC does not immediately reset and there is no slip condition or no loss of drive felt, perform 3 to 4 wide-open throttle accelerations. If the DTC does not reset, replace the valve body (not the solenoid valve body) and re-evaluate operation.

 

Internal Transmission Components

If DTC P2714 resets, check if there is no forward motion but Reverse is operational; a slip under heavy acceleration; or if the DTC or the concern is repeatable.

In addition, check for a drop in primary and secondary pulley pressure due to a leak. Primary and secondary pulley pressure drop during an Auto Stop event. The pressure during an Auto Stop event should be around 400 kPa. If the pressure is below 300 kPa, there may be a piston seal leak.

If there is a loss of drive, slipping, the fluid has a burnt odor, or any of the other listed indicators are present, disassemble the transmission and inspect the edges of the forward clutch piston for damage. (Fig. 26)

 

Fig. 26

 

If the forward clutch piston is damaged, replace it along with the forward clutch fiber plates and the forward clutch steel plates as needed.

If the forward clutch piston is not damaged, inspect the pump for signs of internal wear. Wear may be found internal to the primary pulley bearing bore. (Fig. 27)

 

Fig. 27

 

Any signs of wear may indicate that the primary pulley bearing has spun in the bore and is allowing the turbine shaft to become off center. If this occurs, there may be a pressure leak and the transmission may need to be replaced.

TIP: The primary pulley bearing is installed on the inside of the case on the primary pulley, which cannot be accessed for inspection. Inspection of the pump for DTC P2714 and no concern found with the Forward Clutch Piston is critical to proper diagnosis.

Refer to #PIP5819 for additional information and part numbers.

 

– Thanks to Bill Alley