Hi there. I bought my 2001 XJR approximately a year ago and, although I absolutely love the car, I'm trying to get to the bottom of an annoying vibration -it kind of takes the edge off an otherwise fab driving experience. Any advice very much appreciated!

It comes on at 50 mph through to around 75 mph and manifests itself as a deep rumbling vibration, as though it is caused by something with considerable mass out of balance. There is no discernible vibration felt through the steering wheel, and the vibration level does not change when the brakes are applied. It also doesn't go away if I put the transmission into neutral and let it coast. It is most noticeable when decelerating gently on smooth roads.

I have looked across various forums and have learned that there can be many causes, most of which I believe I have addressed- namely:

New (quality) tyres fitted all round and wheels balanced properly
Prop shaft re balanced
Diff replaced for a rebuilt unit, as the old one was leaking slightly and fairly noisy.
Wheel bearings & CV joints appear don't appear to have any excessive play.
The prop shaft UJ's and centre bearing all appear OK.

I can only think that there must be play in the driveline somewhere, or that possibly the torque converter is out of balance - though I can't really see how that could have changed since the car was manufactured. The car is a Japanese re-import with approx 50,000 miles on the clock, I am the first UK owner. It was serviced before I bought it, but there is no other service history with the vehicle - not in English anyway!

If there are existing threads on the forums I am happy to be pointed in the right direction.

Many thanks in anticipation.

 

An out of round wheel is a out all that is left to be checked.

 

Prop shaft center bearing maybe? The bearing is probably fine at that mileage but it's mounted in a rubber isolator which could be dry rotted?

 

I agree with Randy and Nilanium on their ideas. The outer circumstance of the wheel may appear true, but the inside lip can still be out of round. Having a road force balancer would be your best bet but a lot of shops won’t have them as the cost is substantially more for those machines.

As far as the driveshaft, in addition to what Nilanium said I have also seen the center support bearing sag and that can cause your driveshaft angle to change and cause vibration. For example, if the engine and transmission mounts are new, that can change your angles a lot.

Putting your transmission in neutral while the vibration is occurring and it doesn’t go away excludes your torque converter/transmission internal mechanicals being the cause of your vibration. Your driveline angles are still in play with the vibration occurring and the transmission in neutral.

Just because your car only has 50K on it doesn’t exclude all the other items from wearing out. Think about this, the rubber engine & transmission mounts have been carrying all that weight for roughly 22 years and will sag over time. The same goes for the center support bearing. The imaginary line going from the harmonic balancer bolt to the tail shaft of your transmission cannot line up perfectly to the pinion nut or you’ll have a driveline vibration no matter what vehicle you have.

 

tranny mount

fulcrum bearings

center support

flexy disc

 

UJs in the rear shafts? although my experience of them in prop shafts is coming off the power changes the vibrations.

 

Thanks all - very helpful. The vibration feels like it’s coming up from under the seats in the middle of the car, so play in the centre bearing/rubber support could well be causing the prop to whip around like a giant metal skipping rope. Another day over the pit beckons!

Will report back and let you know how it goes.

 

Maybe this helps - maybe not:
I did have vibration troubles on a Jag, when I bought it and I fixed it - BUT it was a X-Type. I also felt the vibration in the steering wheel and it started at about 75km/h.
It could well have been the front drive shaft bearings only, but I replaced both front drive shafts (The X-Type is a FWD!) and this solved the issue for good.
So it could be your rear drive shaft bearings (RWD) or complete rear drive shafts - and I would expect that you cannot feel the vibration in the steering wheel (while I could), due to the FWD/RWD difference... But if you are really sure that the vibration is not coming from the back, but from the middle, then yes - it sounds like the propeller shaft.

 

Yes, it would have been nice to know the noise/vibration placement
in the first post instead of shooting in the dark.

 

No dirt or mud on the prop shaft? Might also try greasing the zerk fittings on both output shafts just outside the differential. Engine and tranny mounts might be collapsed . .

 

Good call from Jhartz. I totally forgot to have a check for some kind of grease nipples on my X308.

Here is a thread from the X100 forum, so that I know roughly what I am looking for - there is a picture (so maybe it looks like that on the X308, maybe not):
https://www.jaguarforums.com/forum/x...estion-146648/

And Don wrote about that in 2018:
https://www.jaguarforums.com/forum/x...ttings-197051/

 

Meanwhile I crawled under my X308 and had a look, what's there:


This must be the part, which would have had grease nipples, if it were an older Jag. But no crease nipples there - just grease...


...thus I added a bit more grease on mine. Maybe this would help with your vibration woes, not very likely though.


And towards the rear end the propeller shaft you'll find this rubber part. Just have a look at yours, to check, if everything there is as it is supposed to be... Cause if that is worn out and wobbling around, this would explain an inbalance...

 

Peter, that seems a bit odd there is no grease fitting there. I am sure
you checked all four points on the u-joint. The Duchess has them installed
and I notice replacement parts also have them.
iD Select® 215-0178 - Greasable U-Joint (carid.com)

 

Randy, what can I say? You saw my pictures. So unless the grease nipples fell off the car, I have a feeling that my 1998 3.2L X308 does not have any...

 

some cars just don’t have them

wether is factory or service items idk but consider yourself lucky if they’re not there

 

Thanks everyone for your comments and advice. The issue turned out to be the nylon bush that keeps the prop centred on the diff. It was damaged and not locating snugly on the diff spigot - see photo of the offending part.

Unfortunately the part wasn’t readily available, so I ended up swapping the prop out for a second hand unit (thanks to https://www.autoreservejaguar.com/jaguar-parts.html) which cost around Ł95 delivered.

Now she is back together and running like a sewing machine.

 

Thank you for sharing that. I never would’ve thought about that one. How was the flex disc at the pinion?