Any ideas would be welcome in relation to a problem I have with my 2003 XK8. Basically on a constant throttle at around 70mph I get a vibration through it that feels like something, probably at the rear, is binding a little. It certainly doesn't feel like a wheel out of balance type vibration but I do also get that sensation if accelerating gently at around 50mph. The 70mph vibration goes if I shift the gearlever to 5 or accelerate and the car feels fine at 80mph plus (on private roads of course). Simiilarly, harder acceleration at 50 and the vibration isn't there.

I initially wondered if it was a brake binding as I recently fitted new discs, shoes and pads at the rear and the n/s was binding slightly after that but have now sorted that and the vibration is still there. It certainly seems to be worse when it is fully warm. I am wondering if it might be a wheel bearing, but they are fairly new and not making noise under other conditions, but it does have the wheel bearing failing type feel to it. Otherwise I guess I need to start worrying about the diff or gearbox

What can I look for?

 

After eliminating brakes and wheel bearings as a possible cause, it's worth checking the 'A' Frame bushes (RH arrowed in red) for wear before moving on to diff or driveshaft.


(click on the image to enlarge it)

Worn or split bushes allow metal to metal contact with consequent transmitted vibration.

Graham

 

Thanks Graham,

I have a feeling it is a wheel bearing, I had the car up on axle stands yesterday evening and there is quite a lot of play in the wheel and it does have a rough sound when rotating it - strange because whilst driving that is not evident other than as I described it before. I had sort of discounted it originally as they have been replaced relatively recently.

 

I had a rear wheel bearing fail on an XJ40. It wrecked the aluminium hub carrier in the time it took to me to pull over and stop on the hard shoulder on the A1(M) a few miles south of Wetherby. You'll know the area - not a good place for a breakdown or for getting a 'three wheel' Jaguar onto a recovery vehicle!

Graham

 

I know the area well. I had recovery home from quite close to their with a failed front wheel bearing in a Mini once - I'll keep away until this one is rep!aced! It's booed into the garage for Wednesday for them to look as I don't have time at the moment.

 

Andy,

Please let us know the outcome. I've got a so-far-unexplained noise in the same area of the car that has much in common with yours:

- most noticeable when the car is fully warm,
- when this noise is present, it depends somewhat on throttle position.
- seems to be coming from the differential or right side half-axle,
- rotating the rear wheels with the car up on jacks produces a slight "rumble", a gear-like sound ... synchronous with wheel rotation, rather than crankshaft rotation. (this noise, under these conditions, is way too faint to hear with the car running),
- new rear wheel bearings recently.

I'm hoping that, with a little luck, your garage will diagnose my problem as well as yours.

 

Sounds exactly the same as mine Dennis, I've just dropped mine into the garage for them to look at the bearing (they are the ones who fitted them) so will let you know. I'm away for the rest of the week and weekend so should find out when I get back.

 

Update time - I have collected the car from the garage where it has had a second-hand hub fitted. The bearing had been spinning on the inner shaft and it seemed there was damage to the main hub carrier too so rather than try to replace the bearing (which actually looked OK but obviously wasn't working properly based on how it had spun) it was easier to replace the whole lot. Whilst the car feels a little better unfortunately it hasn't solved the vibration which started this discussion.

I need to look at the bushes Graham has indicated but having had a chance to get underneath it today whilst it was over a pit at the garage there is a little play in the rear gearbox mount that someone else suggested but the vibration definitely seems to be more rearwards than that. I wondered about the oil level in the diff but there is no indication of a leak from it at all so hopefully not that.

But basically, still puzzled!

 

Another update - took a while to sort this but it was the gearbox, or more specifically the torque converter which was the problem. I had a replacement fitted today and the vibration has gone and I didn't get the noise on the way home.

A bigger job than I had hoped for initially but I should be able to enjoy the car again now!

 

Andy,

Good to hear your found the cause of the vibration. I've added 'RESOLVED' to your thread title.

Graham