Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Control of Shift Operations
During a shift operation, certain elements are released while others are actuated. Ideally, this process takes place simultaneously (synchronously) to avoid jerky shifting.
The time for the shift operation should remain within the time limits provided.
When the shift operation is controlled conventionally, the pressure buildup and reduction at the shift elements are set and defined for ideal conditions (synchronous shifting).
As there is no way of influencing the control in the event of different levels of wear in the shift elements, when the transaxle has been used for a fairly high mileage it is possible that the pressure buildup and reduction may no longer be synchronous.
The result or premature pressure reduction at the element to be switched OFF is an unwanted rise in the Turbine Shaft Speed (TSS) as the element to be switched ON cannot transmit the input torque.
The result of delayed pressure reduction at the element to be switched OFF is an unwanted decrease in the TSS as both shift elements transmit the input torque. In the process, the torque is transmitted to the transmission housing through internal locking.
In both cases, a jerk will be felt during the shift operation.
In addition, wear in the shift elements leads to a lengthening of the shift operation. Therefore, shifting takes longer when the transaxle has accumulated a higher mileage.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.