Parallel Hybrid Truck (PHT) Transmission Operating Characteristics - keywords chuggle hybrid performance poor power surge TCC

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Parallel Hybrid Trucks (PHT) may have a customer perception that the vehicle lacks power on acceleration, surges and or chuggles up inclines and lacks power when in reverse and 4 wheel drive.

Unique to the M33 is the torque converter clutch lockup that occurs very early. Once locked, the converter smoothes out driveline disturbances and provides coast-down regenerative braking. The torque converter clutch engages (or, in some instances, permits a controlled, very low slip mode) in second and successive gears to help prevent any additional pump and turbine heat buildup

Results of the early TCC engagement may be a surge when tipping in and out of the throttle, surge or chuggle under load and light throttle input. Also due to TCC being applied it will take more throttle input to accelerate and seem to lack power. The lack of power in Reverse with 4 Wheel Drive Engaged is a result of torque limiting to the Front Axles.

The above conditions are considered operating characteristics and the vehicle should be compared to an identical build vehicle prior to any repair attempts.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.