I have my IRS out for a brake overhaul and differential replacement.

I was a bit surprised when I found the inner fulcrum mounts very loose....'floppy loose' to be more descriptive. These are item #5 in the illustration below

Wishbones and Mounting-Rear - Parts For Series III Saloon | Jaguar Classic Parts UK

Can't say that I've come across this before.

The bolts were prevented from totally backing out thanks to the safety wire. I dunno know how long they've been loose. The car has 170k miles. Maybe this accounts for the clunk noise I've heard a couple times?

I'm not an alarmist but it's conceivable that an outright failure could have occurred....eventually.

Anyhow....just a heads up. Something else to check for. With the car elevated and the tie plate removed you could probably get a long pry bar in there and check for looseness.

Cheers
DD

 

This is why I'm no fan of safety wire these days. I use Red or Blue lock tight appropriately, nylock nuts and lock washers where applicable.

Safety wires is difficult to actually do it right. Many mechanics, home and shop, really dont know how to. Unless a person has been on a racing team and learned the "art" chances are it's not right. A properly done safety wire is a thing of beauty though.

 

Can it be that the needle roller bearing seized up years ago and the wishbone has been pivoting on the fulcrum mounting which it should not do, of course !

The XK of the late 90s had a cast aluminium front subframe with trunnion bearings on the upper wishbone with a rod that the bearings fitted onto, the whole thing being bolted-up with nuts each end. Some owners of high milers, and some not so high have found that the trunnions seized and the rod too the wishbone rotation and gradually wore out the housing in the casting.

So, Doug, could this be your syndrome as well. I don't know much about the upper trunnion housing; is it cast iron or aluminium ?

 

Doug,

Common as morning coffee.

Every Jag from the S Type, up has had that issue for me.

The bolts loosen a tad, the working of on and off the throttle works the shims out, and then its sloppy loose.

Our S2 Daimler had one bolt sheared off, like a guilotine.The wire helped to a point to stop the open bolt falling out, but the second bolt is trapped behind the spacer tube and can only undo so far.

YES, that would be the clunkies you hear.

I use full circle shims, in lieu of the horseshoe syle, and locktight. Never had issues after that.

Check the top 4 bolt holes in the cradle, they crack up there from the working of the diff centre.

 

It's a LOT easier when you have that much room to work with

Cheers
DD

 

And once the shims fall out it can only get worse!



Another odd thing is that, on each side, one bolt is longer than the other. I haven't investigated why. If that's typical, I've just forgotten. Been quite a few years since I've 'been there' !



I'll do the same but, because I sorta enjoy doing it, I'll use the safety wire as well.



The uppers were not finger loose but I didn't have to do much more than set the wrench on 'em to remove 'em. No cracks, though

Cheers and thanks
Doug

 

Nothing seized, no. Years of the typical leaking stub axle seals ensured that everything has been well lubed for the last 32 years

Cheers
DD

 

Happy mechanicking !

 

Hmmmm. It seems to me that two smallish bots are subjected to a lot of load. In tension and shear!!! But, other than a clunk on some, it seems to work.


Am I going to jack up mine, remove the bottom plate and pry? Not likely.


Were I to do so and found a need to fix, I'd consider two changes. A single strap with two holes to replace the open end shims or any washers. More friction surface?
and failing room to safety wire, a single "mechanics wire" tying the bolts together.
Old Ford V8 flat heads used that method to secure the nuts and studs on the center main bearing. It worked.


I'd do some thinking about a thread locker, Loctite or similar.


Carl

 

For full circle shims, you can use IRS camber shims. Cut the corners out.

Good luck,

Rob

 

As I have Nix well and truly jacked up at the moment, I'll add this check to my list.
Thank you, Doug, for posting. I haven't heard anything questionable back there, but while I'm at it.......
(';')