After I've driven for around 10km/6 miles, I hear a clunk in the rear end whenever I start off after having stopped for some reason. Sometimes the sound seems to be on the right, sometimes on the left and at other times in the middle. I do have a degree of diff whine, but the owners manual tells me that a certain amount is normal and the whine I'm experiencing is not particularly worrying to me - not that I would know what's normal and what's over the odds.

My '91 XJ40 also has the hydraulic rear levelling system and, having read posts on this forum that suggest one should feel the rear end rise on starting the car, which I don't, I'm now not certain that that system is working.

Would anyone have any ideas as to the origin of the clunks?

Thanks in advance.

 

Rosspot:
I thought by 1991 these cars were no longer fitted with the SLS system; I know that was true in the States, but perhaps not Australia. Those that had the system by now, from what I've read, have usually long since failed and were retrofitted with a traditional spring configuration. Are you sure yours hasn't been?

Regarding the clunking... I would definitely have somebody look at the differential and do an oil change. That would also show whether there are bits of metal sitting on the bottom of the housing, proving the significant wear that they will probably find. The differential on this car is a notorious weak point; and I cannot imagine that rebuilds on all of our cars is only a matter of time... I'm trying to stave that off by gentle driving and regular fluid changes!

I realize that's not especially technical or probably helpful. But it's what I know. Hopefully others with more experience will chime in!

Scott

 

I'm reasonably sure my car still has the SLS, although the oil reservoir also serves the power steering system which would explain it still being in place. I'll get that checked out.

I have had oil changes, but I can't say that the oil in the diff has been changed since I've owned the car. It's due for a service, among other things, so I'll make sure that that is also checked out.

Thanks for dropping by and replying to my post.

 

Your clunks could simply be due to worn suspension bushings.

 

Rosspot, check the top plate of the rear suspension (shock and spring pan) mounts. It's possible that the top of the shock absorber rod, where the steel tube bushing wears through the steel plate with age and makes it sloppy and very clunky. You may need either new plates or have a good welder try and repair them... if they are badly worn you will also need new shocks and bushings This was the case with my '88, I am assuming your '91 has the same set up

 

Thanks for the info, Jagfix38. It seems to make sense. I'll be putting my car in for some work in the next week or two - I'm a total dunce in respect of all matters mechanical - and I'll mention your reply to the mechanic and ask him to thoroughly check the rear suspension.

 

The SLS was fitted to XJ40 sedans from 1988 to sometime in 1993 here in the U.S.
I have posted several TSBs for diagnosing and/or deleting the SLS.

There is also the POWER HYDRAULICS booklet in .pdf in the large file download.

bob gauff