As the UK's leading supplier of replacement commercial vehicle transmissions parts, H L Smith have a wealth of information about parts and maintenance of your commercial vehicles.

If you have a problem you need to resolve, try our FAQs. If you can't find what you're looking for, please contact us and we'll  get back to you as soon as we can.

Problem with Allison automatic gearbox - no power to selector

Check the small blade fuse connected direct to the battery.

Back to top

Advice please - I'm unable to engage drive. The selector just beeps.

H L Smith recommend that you check:
1. The throttle pedal is returning back to the top.
2. The tick over RPM is not set too high (should be approx 600 rpm)
3. Throttle position sensor is connected and not damaged.
4. Then check the diagnostic codes.

Back to top

Problem - Selector says drive, but I have none, why might that be?

Does the oil level drop slightly as you engage drive?

If it doesn't, the engine drive flex plate may have sheered.

If the oil level does drop, either:
1) the oil pump drive hub may be damaged, which in turn will give you no main pressure
2) The clutch pack may be damaged to the extent that it can no longer hold drive
3) Check diagnostic codes for information.

Back to top

What should I do if the “Do Not Shift” light is on during vehicle operation?

The light indicates that a diagnostic code has been logged by the ECU. Check the system straight away for codes, which should indicate the transmission fault. Diagnostic codes can be recorded without activating the “Do Not Shift” light, so please remember to check for codes on a regular basis to maintain your transmission life.

Back to top

Back to FAQ list.