Driveline lash, what is normal?
 

There are certain circumstances that give a decided clunk whe shifting, usually downshifting. Say when rolling gently to a stop the car will sort of splat into low gear causing a significant clunk. Or as the other day in variable traffic where speeding up and slowing down a lot, it happened a time or two at higher speeds.

6spd ZF, 70k miles, fluid service was done about 5k ago and the clunk is the same before and after.

It "feels" like slack in the driveline but given the different profiles the transmission can use I'm not truely sure how to tell the difference between that and a harsh shift.

Is it just that I just happen to change the throttle position right as the tranmission is about to shift and confuse the algorithm? Is there possibly something more sinister lurking?

Thanks

I have an 04 xk8 with the same mileage as you and it does this same thing. Always has seemed like some slop in the drivetrain somewhere, but I have never really been that concerned. I have had the transmission fluid changed (not for this, but just preventive) and TCU updated, never made any difference. I have always just suspected it was xk8 normal.

I had the same issue with my 2005. When it was still under warranty the dealer changed the driveshaft, replaced the rear gear box and re-flashed the software. There was a change for a few months and then back to the occasional clunk on down shifting too a stop. I have had the car for 4.5 years now and no "real" driveline problems beyond the occasional clunk. According to Jaguar the problem is related to the ECU/transmission software and any sudden changes in driving style.