I have heard good things about the ZF transmission but right now I am having doubts, my 2006 XK8 convertible with 88K just started having a problem. Highway driving when I accelerate it seems to lag and then kick in, I am driving around 65 - 70 mph, it happens every once in a while. Then about a month ago after feeling it slip, mind you this only happens after an hour into the journey the Transmission fault light came on. When I reached my destination I shut the car off started it again and light was out. It seems to only happen after driving a while and after I feel the slip. I took it to my mechanic who replace the valve body, he said to start with that and there was a 50/50 chance it would fix the problem, if not it would need a rebuild. When I left the mechanic it was working fine for while but then it slipped again. No light. But on another long journey two weeks later driving with my foot on the pedal keeping a steady speed the speedometer needle just increased on it's own, then it was bouncing up and down erratically for about a minute! Never saw this before. At that point the transmission fault light came on, the check engine light as well as the ABS and DSC System Fault but the funny thing is the car seemed to be riding okay about a half hour the rest of the way on the highway. I had read a post by Razorboy saying he had a transmission fault and by a fluke found by fixing the wheel speed sensors and wheel bearings it solved the problem. I am at wits end if anyone can help or know what this sounds like? Thanks.

 

How old is your battery? Failing batteries are known to cause erratic operation in these ZF transmissions....

 

You would need to read the diagnostic codes to be more sure of a path forward. It would have to be a Jaguar/Land Rover reader, and available when the codes are there. Stopping the car and restarting it might be too late for a complete list.

I would start by checking on the reluctor/ABS rings on the rear hubs, especially driver side. These are used as a road speed input parameter into the shifting logic, in conjunction with the output shaft speed. They occasionally work themselves loose and confuse the heck out of the shifting logic, leading to all kinds of codes. You can raise the rear of the car on ramps and reach out to the rings with a blunt/plastic tool to see if they are still _solid_ with the axle. They are on the wheel end of the axles, just below the ABS sensor of course. The fact that your speedometer needle jumped all over the place is the main clue here.

Best of luck, keep us posted.

 

I think it's about 4 years old, I had the original one in up until that time which was amazing. I will check it and see, thank you.

 

Thanks so much for your advice I will relay this to the mechanic, as I cannot afford to have a dealership work on it and it's extremely helpful to exhaust all possible solutions, knowing what a rebuilt transmission would cost with labor.