I have a 2004 XK8 that shifts smoothly when cold but after several minutes of driving, the initial shift from start to the next gear is accompanied with a jerk and a clunk. The rest of gear changes are smooth. The car has 69,500 miles on the clock. Thinking of changing the tranny oil. Your thoughts?

 

1. do it
2. please post in the correct forum - someone may move this thread

 

I've moved your question from General Tech Help to XK8/XKR forum. This is the place to post technical questions about your model and you will also find many threads on the same topic here.

Graham

 

If you do not know the history, look into the replacement of the filter/pan as well as the connector sleeve (fairly inexpensive plastic parts to buy). Consider Mercon SP as the fluid. Make sure the shop knows how to do the temperature-based refill procedure (no dipstick here). This trans is widely used (including Ford models), so the expertise is out there. At a later point, you can do a simpler flush/refill to get rid of the rest of the old fluid.

If shifts are still not smooth, consider re-setting the adaptations. This is a drive cycle performed under the supervision of the Jaguar/Land Rover SDD factory software.

Separately, your transmission could be running really old code. That code can be re-flashed using the factory SDD software with the appropriate cabling.

Altogether, this 6HP26 transmission is well known, and there are other services/parts to throw at it for various problems. The bridge seal and the 3 rubber tubes are listed (mostly on BMW applications), but the valve body has to come off (trans stay on the car, so not a huge deal). You can get new solenoid valves, or even a rebuilt valve body but this is more $ obviously. Lots you can do under some form of a budget as the trans does not have to come off the car for every little thing.

Best of luck, keep us posted.