Problems with your truck transmission? Try our tests

Here are also some involved tests that you might consider, before calling an engineer to work on your vehicle:

Display indicates a fault

Always a good starting point.  As with any car, the vehicle’s dash display might well carry the first indication of where any particular fault might lie.  You may be able to cross reference this yourself with any manual you might have.  If the fault is serious, it can still help when you phone any service centre, since you will already have this information to hand, which will immediately help the engineer to diagnose the problem and advise on a solution.  

Splitter group test

With this test, you start the van and let the air build up to its usual optimum pressure. Put the vehicle in manual mode, then put it into first gear… then up to second… back down to first… and back up to second.  Then keep going, with 40 gear shifts from first to second, in order to check whether the splitter synchro is denuded, and it is that that is causing the issue.

In normal operation you’ll hear the splitter changing quickly, taking into consideration the van you’re in and where the gearbox actually is.  However, if you conduct this test and the gearbox doesn’t actually change, then the splitter group is indeed likely to be the cause, in a fault known as “end dogging”.  In these cases the gearbox will need to be removed and properly looked at.

Lubricating the clutch fork

You’ll find you’ll get much more consistent gearbox performance if the clutch fork is appropriately lubricated and freely able to function.   There are two clutch assembly designs, and each needs lubricating in a particular way, with different lubricators.   So whatever you do, make sure you note down the spec of the gearbox, so any mechanic can help with a correct diagnosis and the lubricant needed.  And it is certainly worth checking this with a mechanical engineer because, correctly lubricated, the clutch fork will both help the performance of the vehicle, and also help prolong the life of the clutch itself.

Test the clutch actuator

You can test the clutch actuator itself by firstly removing it.  Then look at the side of the main body and try to find the chamber screw… you’re looking for around a 20mm screw.  If you take this out, you can then push the bellow into the cylinder.  Why?  Well, over time the clutch actuator carries out many, many shifts and that wear can be taking place in the bore of the main cylinder.

A new actuator can hold for hours, with little movement; however, if the chamber is worn down, then the bellow will release quickly.  So after pushing the bellow back into the cylinder, replace the chamber screw and tighten it, then release the bellow itself and watch for how quickly it lets go.  If it does release quickly then that shows the actuator needs replacing, as the cylinder is almost certainly worn.