Hi everyone

Her in cold Norway my XJS relaxes in my garage. Mostly because itīs not very nice to drive. It wobbles and shakes, and itīs really worse at 140 kmh. Its not wheels/rims. Front upper balljoints, wheel bearings and shocks are new. Itīs not engine rpm related, and not load related. Gone trough everything on the car for the last 2 years. Everything looks and feels as it should.

Anyone know about propeller shaft yoke alignment on these cars? or other ideas?

Best regards from Norway...

 

Model? Year? Engine?
Greg

 

XJS, 6.0 L, 1994 coupe

 

So further interrogation:

1. off-load on the over-run the vibration is there just as much as on the power?
2. does this happen at all speeds?
3. does it increase in frequency the faster the car is going ie speed related (you have said it is not load or engine-RPM related)?
4. have you any feeling from where the vibration seems to originate (eg under seat, from the back, from the front)?
5. is it more of a fairly low frequency "wobble" feeling or quite a high frequency vibration?

If it is lowish frequency and is speed related, my money is on the propeller shaft being shot, or its UJs. The propshaft is one-piece, but it is actually made up of two tubes bonded together with rubber, and it does fail and produce this sort of symptom. New ones are available from Jaguar and are not that expensive, surprisingly. After that there are other things such as:

• gearbox/engine mounts not fixed properly
• gearbox output shaft bearing failed
• differential unit coming loose from the cage
• differential-attached brackets to which the bottom rear wishbone is attached coming loose
• bent rear driveshaft

I would do the prop and check the engine and gearbox mountings are correct and 100% first and then see. It sounds tome, as you said the vibration is independent of RPM and load, that the cause will probably be gearbox tailshaft or backwards. The other things mean rear axle out - all quite doable at home in your long winter evenings - as long as the garage is heated!
Greg

 

Thank you Greg, for replying

The vibration starts being bad at 140 kmh. its still the same even if I put it in neutral. Had the prop shaft down and the UJs ar good. The strangest thing is that it seem to getting worse
after driving a while......
do you know how the prop shafts yokes should be in position to each other, there are no marks in the splined end...

 

By the way.....
gearbox mount is new, all rubber looks fine and differential is tight. (of course for some reason its input is off-set to the right)

 

Normally propshaft yokes are at 90 degree to each other, so when one end is one way, the other is the other; but I cannot be 100% sure without looking and that involves a decent bit of dismantling that I am not going to do! Maybe someone like Grant, who knows everything there is to know, can tell us for sure? If not, I have a spare old one in the loft and will look at it.
This sounds more and more like the prop being out of balance to me. I happened to me last year with an annoying lowish frequency vibration at about 50 MPH and drove me mad before I nailed it with a new prop, thanks to a suggestion from Brakebuster on this site. JCP lists three different props for the 6 litre dependent on VIN number:
http://www.jaguarclassicparts.com/uk...shaft-assembly
So it would be worth getting your VIN and contacting them to see what is available. In the UK there are loads of specialists who can fix and rebalance propshafts, or even make you a new one, surprisingly cheaply all things considered. If JCP do not have any new ones, David Manners or other specialists like SNG Barratt may well have something suitable.
Greg

 

Thanks a lot Greg.
I will concentrate at the prop shaft. On my car both yokes are in line with each other, but since the input flange of the diff. is off center, I suspect the shaft yokes should be in a certain position to each other, but thats just a very diffuse thought.

 

I believe the yokes each end should align. ie. Be on the same plane.
Pretty much the same as the halfshafts.
The only vehicle l have come across with deliberately out of phase prop shaft was p38 range rover although there might be others.

 

I know you said its not Wheels or Rims but it could be something Simple, like the Wheels need rebalancing.

It might just be worth a shot?

 

Baxtor is 100% correct. I have just looked at the prop I have in the loft. The Y shaped pieces of the UJ (yokes ?) that are FIXED to the ends of the prop are in the same plane. Apologies for my previous suggestion that they were not.
Greg