Possible causes of impact when engaging reverse gear on a DP2 automatic transmission:
1. Low transmission fluid level:
* Check the fluid level on the dipstick and add if necessary.
2. Contaminated transmission fluid:
* Replace the fluid and filter, especially if the transmission has not been serviced for a long time.
3. Line pressure too high:
* Check the line pressure with a pressure gauge and adjust if necessary.
4. Faulty reverse gear pressure valve:
* Replace the valve as it may be sticking or not generating enough pressure.
5. Worn or damaged reverse pistons:
* Pistons can wear out over time, causing leaks and insufficient pressure.
6. Faulty valve body:
*Bypass valves inside the valve body may be faulty, resulting in unstable pressure.
7. Faulty output shaft speed sensor:
* The sensor may give incorrect readings, causing the transmission to shift incorrectly.
8. Faulty electronic control unit (ECU):
* The ECU may be faulty, resulting in incorrect commands to engage reverse gear.
9. Wiring harness faults:
* Check the wiring harness for damage or corrosion that could affect the signals.
10. Worn rear gear drum rubber seals:
* Worn seals can cause pressure leaks and make it difficult to engage reverse gear.
Note: It is recommended that you have a qualified mechanic diagnose and repair the root cause of the shock when shifting into reverse.