My 'new' XJR has a nasty shimmy from the back end when going over bumps. I've read all about the rear subframe bushes and rear shock absorber issues but there seem to be none of the associated knocks that go with them. Could it still be down to one of these or is it something else?

 

Welcome to the forum entwistlecymru,

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As the shimmy only occurs when going over bumps, it's unlikely to be wheel balancing or a distorted wheel rim. Shock absorber Upper Isolator and Lower Bush are usually easy to spot.

There's a lot of wearing parts in the rear suspension Favourites are:



1. Sub Frame Bushes (arrowed red)
2. Differential Strut Mounting Bushes (arrowed green)
3. Wheel Bearings (arrowed orange)
4. Pivot Bearings (arrowed blue)

You need to get the load off the rear suspension to check for wear. For (1) and (2), support the body under the rear jacking points. For (3) and (4), jack up each side of the vehicle in turn under the rear jacking point.

Graham

 

the above is perfect, I have nothing to add except that I'd lean twards wheel bearings. rear tires wearing uneven ?

 

As it happens the R/H rear tyre is a little 'bare' but I just put that down to the last owner smoking the tyres up. I've ordered some bearings anyway but surely I'd be hearing rumbling or whining? I noticed they're two taper roller bearing so is there some adjustment to be had?

 

Usually, but you can't count on that as the only indicator. Get the wheels off the ground and check for slop by rocking the tire at 12 and 6 o'clock positions



Adjustment is by selective shims between the bearings. There should be a couple thou pre-load. That is, a bit less than zero free play.

Cheers
DD

 

I'll check for play in the morning. If I change the bearings will I need to reshim or is it a case of swapping the old shims? Where/how is the free play measured?

Keep the replies coming gents - its all helping

 

Often there's no need to re-shim but it's entirely dependant on the replacement bearings and how far they are/can be pressed onto the shaft.

I think the service manual is linked in one of the "sticky threads" at the top of this section. You can look up the procedure.

Cheers
DD

 

ya it should be obvious once the rear is lifted, 12 and 6 firm grip and rock it, you'll feel play if the bearings are bad. GL

 

It all looks straight forward enough but I can't help thinking I might as well just do the whole back end - 150k on the (apparently) original shocks and bushes. If I've got it apart I may as well do the lot.

 

Definitely the best approach on a vehicle with 150K miles if time and funds allow.

Crunching the numbers and saving one more tyre being scrubbed off makes economic sense.

Graham

 

Well Gents, I've bitten the bullet and order bearings, bushes and shocks for the back. A friend is taking it in tonight so it should hopefully be done by Wednesday. I'll see how much of a difference it makes then! I've also bought a set of new tyres on wheels from a local tyre fitter friend (who happens to have an XJ40 and X300) so they'll be replacing the knackered Dunlops on the back and rock hard 'Primewells' on the front. Next month I'll be curing the various little oil leaks and rebuilding the front end, which brings me on to my next post...........

 

The fault turned out to be the inner rear wishbone bushes - completely knackered! I'm still waiting on ARB bushes from Jag but at least when the axle goes back on (Did I say the whole assembly is off?!) it'll be as good as new!

 

Well, this reply won't help anyone in the future as all I did was rebuild the entire rear end of the car. However, I can confirm if you spend £800 in parts with Jaguar, your shimmying X300 will be transformed. 18 years of wear hadn't been kind and it now feels brilliant - I can see what all the fuss is about!