Dear All, For some time my XJR has had a slight clunk ocasionally when taking up drive which feels like it is coming from the rear of the car. It has now got worse and more consistant. I have previously tried pulling on the propshaft to see if the rubber around the centre bearing had failed but there was no movement and the foam rubber bush in the gearbox mount is only a few years old and in good condittion, with only the normal up and down movement on the springs. The round rear subfame bushes are in good condittion (solid on the XJR). I have a pair of rear subframe mounting rods from a spare rear end which I have fitted new bushes to and plan to fit to see if that helps. The diff itself is not noticably noisy although my exhaust is blowing slightly at the moment so may mask the sound.
If I turn one rear wheel by hand whilst the gearbox is in park and an assistant holds the other wheel still, how much play would you expect in the diff? For information the locking action is very weak but I have been told that it was set up that way when they added traction control.
Any comments apreciated,

John

 

I am dealing with a similar problem, are you also getting any shudder through the driveline when traveling around 80 - 100km? From talking to a couple of jag mechanics they have led me to believe it is the rear coupling, like you i checked it out and from what i can see it looks fine, but thinking of replacing anyway just to be safe.

 

It may, or may not be your problem, but after going through several things, such as you have, I replaced the rear shocks. The upper bushings were almost non-existant. The car felt like the tires would get out of balance, and then back in balance. Replacing the shocks and bushings took rattles out of my interior, made the car so much smoother. I still can't believe the difference it made.

 

From previous Jag experience, you need to check all your UJ's in the driveshafts and prop. If any can be greased try this, and see if it changes it in anyway. Driveshaft UJ's will clonk and give vibration similar to out of balance wheels.

Steve

 

Thanks Guys,

Interesting comments, I do sometimes get a vibration like out of balance wheels when I first get on the motorway ~ 100KPH which then goes away after say 30 seconds and stays away for the rest of the day.
I replaced the bushes in the rear diff support rods over the weekend and havent had chance to test it properly since.
I have also noticed that there is some slight in and out movement in the gearbox output flange. That has worked loose before so I will refit it with some loctiite on the splines as there is some slight rotational movement too.
How obvious is a worn UJ, ie would I see feel the movement when turning the wheels / prop by hand?
I might try changing the top damper bushes if I can undo the four small nuts holding the spring carriers, they are quite rusty on my car!

Regards,

John

 

To check freeplay in UJ's, you need move shaft up and down at each joint to look for free play, rotate 90 degrees and do the same again. There should be none. if you see ANY the joint needs replacing.

Its a bit more difficult on the drive shafts as when the car is jacked up the shafts are under load(suspension dropped), so best checked up on a 4 post ramp or car on wheel ramps.

Steve