Hey everybody...

As a few threads lately had been started regarding the front axles of the XJ-S/XJS rotting through and people saying that the axles are the same (I was amongst them ), I have found some differences...

Firstly:
all XJ subframes (XJ6, XJ12, XJ Series I, II or III) are the same as the XJ-S/XJS. No matter if V12, 3.6l or 4.0l. The subframes are the same.

BUT the rest is slightly different. I've been comparing parts to see what I can/should keep and what I have to part with. This axle is from a series II XJ6.

The upper wishbones have a different shape and have some different shiming compared to the XJ-S. The camber is also a good bit different (as far as I can tell, the XJ-S has more camber in the front as the upper wishbone sits closer to the subframe than the XJ-S wishbone dones - as they are mounted on the inside of the subframe, thicker spacers = more camber). Left is XJ-S, right is XJ6 series II. You can see the wishbone shape is more tapered to the middle unlike the straight XJ-S wishbone halves...



The uprights are very similiar (in my case they lack the ABS hole and toothed wheel on the hub) but have a different hub sealing (compared to my 1989 uprights) so be careful with that!

Last but not least, the lower splash guard for the brake disc (the little plate) is rounded off rather than squared.



Otherwise everything seems the same. The lower spring pans are the same. The lower wishbones look the same too... So if you plan on simply exchanging your axle for one from an XJ (older, newer) make sure you keep these facts in mind! Less camber can result in a less sporty ride. And if you have ABS you will want one from 1988/1989 onwards...

 

Jaguar put some more anti-dive and anti squat geometry into the XJS front suspension, I believe, than was in the saloons at the time the car was being developed, also the car was lowered compared with the saloons, and certain aspects of its handling made sharper compared too, I think. Maybe the differences you show are to do with one or both of those aspects.
Greg

 

Agreed, the cradle/subframes are identical.

A huge mistake I see way too many times is the camber shimming. The thickness of the shims fitted to the FRONT bolt, MUST be the same thickness as the shim fitted to the REAR bolt. This maintains the top and bottom pivot pins in a parallel plane.

Caster is set by relocating the fitted shims out AT the top balljoint, whilst maintaining the same number of shims in total. This caster system carried right through to the X300.

MANY wheel aligners are LAZY, and attempt to set caster/camber using the top bolts, using different shim thickness front to rear. Now, this is fine on many generic cars, GM. Ford, etc, but NOT the Jaguar system. When set this way, the owners find the top and bottom (less so) bushes wear out quite quickly. It is all in the angle of the dangle.

All of mine were wrong at purchase, and once sorted, and top and bottom bushes replaced, I never visited that area again.

 

I have the little shims on my upper balljoints as they were before and how they worked... But before I drive the old lady, I'll be having an alignmemt done - and I'll set it up

 

This training document on Jaguar chassis details differences between XJS and XJ sedan (xj40)

Maybe interesting

 

Doesn't quite help as the XJ40 is on a totally different base

 

I think you are right.

Another tidbit to help future sedan-XJS parts swappers:

The Series III Sedans were made with two different specification upper control arms....so be very careful about mixing and matching. The change is subtle...not something you'd easily spot on simple visual inspection.

I'm sure the info is in the archives but I recall the change being 1983-ish and involving the 6 cylinder cars only. The upper arms were changed to the same part number as used on the V12 cars. The V12 cars used the same upper arms all along.

I think this was related to the anti-dive geometry as mentioned

Anyhow, I may have the details a bit wrong but the important thing is to be aware that a change was made

Cheers
DD

 

And many are so set in their ways they don't want to know.
I normally have the local put the car on the rig and l then take the printout home and move the shims/adjust where nessessary. The guy got a bit cut first time l said l didn't want him to actually do the alignment. You need to watch them on steering rack with pipe wrenches too.

 

Agreed.

Then how many think you are totally crazy when you ask to ensure they use the centreing tool to centre the rack. All they want to do is remove the steering wheel and respline it, DUH.

 

Or they wedge something between the wheel and the seat whilst damaging the leather. Been there, done that...

My poor C30 had some brand new leather seats and the result was, after an alognment, that the leather was badly cracked when the tw*t put the clamp...