My Jaguar XJ8 4L 1997 would occasionally display a ‘Gearbox Fault’ message, which could be reset by turning the ignition off and then on again. As months passed the message was displayed more often and with physical symptoms. This usually involved the car going into limp mode (stuck in one high gear with reduced engine power) or sometimes stuck in first gear.



I suspected that the fault could be electrical rather than mechanical when I discovered that the ‘Gearbox Fault’ could be triggered by moving the gear selector into third or second gear without the engine running. The fault could also be cured for a while if the gear shift stick was put through several gear change movements, without the engine running, before a journey. I suspected dirty/corroded electrical contacts (which were improved slightly by gear shift movement).


I took the ‘J’ gate apart and all was fine there as I could trigger the fault, switching from 4th to 3rd gear without any of the micro switches in the ‘J’ gate moving. The next obvious source of the problem was the electrical ‘Rotary Switch’ which fits onto the side of the gearbox and senses gear positions. I took a chance and paid 70 pounds (UK) to buy a used switch from e bay. I then paid a local gearbox specialist 50 pounds to fit the part. It worked! The problem was completely fixed for 120 pounds which is just as well as the 2,000 pounds cost of a gearbox rebuild would have been unaffordable. I didn’t dismantle the failed rotary switch but guess that it suffered from water ingress and severe internal corrosion.



A new rotary switch from Jaguar would have cost over 400 pounds and would also have been a gamble. The e-bay seller was Auto Reserve in Ilkeston UK.


I hope that this helps.

 

Hi Christine51,

Thanks for posting your success story!

Below is a link to photos showing how I serviced the rotary switch on our '93 XJ40. The rotary switch on the X308 is probably similar. You can clean the gold traces with a pencil eraser and zero-residue electronics cleaner spray and reflow the solder on the cable connections:

Welcome to Jag-lovers - Members Photo Viewing Page


Thanks again!

Cheers,

Don