I am having a major issue with my 1995 4.0 XJS Auto Gearbox, it won't change up from 3rd to 4th gear. This is baffling both me and the specialist who has just rebuilt the gearbox because of this very problem.
A broken roller bearing that had thrown a pin was found although there had been no indication of that fault as it otherwise works as it should. We have tested all the obvious things like the solenoids etc and
it is assumed that it is something to do with the way these gearboxes are electronically controlled. The TCM was swapped with another but this made no difference.
The gearbox is the ZF 4HP24 Electronically controlled. The cars mileage is low, only 45,000.
Any ideas greatly appreciated.