ZF Transmission

Check the stall speed while checking the line pressure
- The stall speed test primarily gives an indication of the condition of the torque converter and the transmission clutches.
Test conditions
- engine must be properly tuned
- correct line pressure
- correct oil level and normal operating temperature in transmission.

Note: Never perform a stall speed test with the line pressure too low.

Testing
- Connect a tachometer so that it can be read on the dashboard. Start the engine Apply the parking brake and step hard on the brake pedal with your left foot. Put the gear selector in the Position D and press the accelerator to the floor.

Note: Max. 5 seconds.





- Read off the highest rpm and the line pressure.
- Let the engine idle in position N for about 30 seconds.
- Put the gear selector in position R and repeat the test.

High stall speed:
300 revs higher than normal.
1. Incorrect oil level. Check the level.
2. Clogged oil strainer. Remove the oil pan and clean.
300 revs higher than normal with screeching clutch or brake.
- Slipping clutch or brake. Dismantle the transmission.
Check:
- For gear position R, mainly clutches C2, C3 and brake B3.
- For gear position D, 1, 2, mainly clutch C1.

Low stall speed:
300 revs lower than normal.
- Check whether the engine is properly tuned.
600 revs lower than normal and poor acceleration at driveaway but normal acceleration above about 70 km/h.
- Defective torque converter. Replace.