Hi, this might be my first post here. I have been waiting and looking for an XK8 purchase. I found one which I rather like, although it has HIGH mileage (120,000). the car runs, shifts, and stops very good but I have noticed that when coming to a stop (EVERY stop) a CLUNK or THUNK noise comes from the rear end just prior to a full stop. I suspect his is not good situation. I'd really appreciate the forum's thoughts on: #1 What the likely cause of the noise is and # 2 ( assuming the car checks out on an inspection prior to purchase) what this convertible is really worth.

Thanks from Colorado !

 

The noise could be anything from a loose brick moving around in the spare tire well to an issue with the axle / brake caliper / transmission etc. etc. etc....

First things first - remove the trunk floorboard and look for loose objects moving around in the spare tire well. If you find nothing, don't purchase that car until you can locate the source of the noise so you know what you're dealing with....

 

You don't mention the year but a common "problem" is the transmission rather splitting into first gear as you come gently to a stop. This is mostly an artifact of the transmission programming in our cars and is a sort of idiosyncrasy that they have.

Fluid changes can help some but I've also found that braking harder to a stop makes the thunk much less likely to happen. That isn't how I normally drive but is an interesting observation, almost as if the car isn't really sure you intend to stop when you are easy on the brakes.

 

Be sure to check for the screw in tow eyelet in the trunk. This thing is big and could be clunking around. I raped mine in a rag. Good Luck!

 

I read a post quite some time back whee this was brought up as driveline lash. I have a 2004 with 75k miles and have this driveline lash clunk you describe. I I recall, it was not too uncommon based on that thread. I find it annoying only when my wife is in the car with me (don't ask).

 

Where is the Reverend Sam when you need him?

 

Thanks for the thoughts guys! I'm going over to see the vehicle again after Christmas and I'll have a look around in da trunk.

Sitting Bull

 

Not a suggestion, really, but more a question for those more knowledgeable. Could this be something to do with the torque converter unlocking? I have on occasion noticed a similar sensation when coming to a gentle stop, which I rarely do. I have lived alone for ten years now, so I do not have an onboard critic.

 

Did you always put this down to a design fault on the XK8? My 2005 one is clunking quite hard now when it’s going into first gear, unless I break hard. Quite worried as it’s getting more noticeable.

 

When its in normal rather than sport it starts in second not first. You could try knocking it into neutral as you stop to see if that takes it away ( removes load on drive train)
Sounds like play in
1/ Drive shaft joints
2/ backlash in the differential ...mine has a little
3/ play in a propshaft joint.

All are easy to find if its up on a lift.
If its the differential dont worry too much just put some thicker oil it SAE 140

I see this is 2012 but may help the last poster.

 

Only when stopping gradually and makes no difference if it’s in gear or in neutral.

Seems to be getting worse !

Have changed gearbox oil, diff oil and there’s nothing in the boot….

Did OP or anyone else have any joy in finding out what was causing this issue ?

Thanks

 

I have a similar problem with the 2000 XK8 i just bought 2 days ago: On the interstate slowing down in heavy traffic from 70 to 50 mph I will sometimes, but not all the time hear and feel a clunk from perhaps the tranny downshifting, but yes I can definitely feel it. Also sometimes in city traffic when I'm only going 40mph and slowing for a stop light I get the same reaction. Any ideas? Is it just that I'm feeling the tranny downshifting or should I be concerned? I've only owned the car for a day and a half so a bit worried.

 

Private sale or dealer ? Time to get under and check the drive line for play in joints etc . I ok check the fluid level in the autobox

 

For me the “thunk” only happens when coming to almost a full stop and when you do so slowly.

When driving in a spirited fashion (I live I South London so most of the time I’m crawling everywhere at 20mph) I was starting to get a harsh change up at 50-70 - but to give everything in order….

I had changed gearbox (transmission) fluid and sump filter - twice - as someone had previously put in what I was told was the incorrect fluid. Someone else said that the “incorrect” fluid was put in as a possible solution to this known issue in the ZF box.

Changing fluid twice was much cheaper than doing a full flush and I was told by a gearbox specialist that this would be ok.

Still did it. So I swapped the rear-differential for a second hand one from a low mileage donor car and checked out all the driveline linkages whilst doing so.

Still did it. So I took it to an independent Jaguar specialist who said the gearbox was 1.2 litres short of oil. This was strange as I’d definitely filled it as per workshop manual…. No sign of leakage - so where’s it been going ?

Independent guy reset gearbox adaptations and told me had to drive for 50-100 miles in a specific fashion accelerating slowly and decelerating slowly so the gearbox moved up and down through the gears and “re-learned” its adaptations.

This is difficult to do where I live but I did it as best I could. Has helped - but it’s definitely still doing it. It’s a 160k car so it’s not a show queen and only gets occasional use so maybe I’ll live with it. But it does bother me.

Next to try will be changing or repairing the mechatronic unit in the gearbox - which is accessible when the sump is off. Also some seals may be letting by which may account for the suspected oil loss - but I’m speculating… I just don’t know at this point.

Second hand gearbox is about £300 which is only just slightly more than cost of second hand mechatronic unit.

Refurbished mechatronic units are available but not sure I want to spend that kind of money…

 

Old thread but I just bought a 2000 XK8 and it has the exact same problem. If you see this let me know if there was any resolution. Tks!!