I have a POS $500 89 xjs conv. Im going to rebuild the rear brakes diff and suspension. I need to know if I can remove and bolt whole assembly in to another xjs or xj. I don't mind spending $1600ish to repair if I can reuse in the future.
Also how interchangeable are the front discs, rotors and calipers?
Any info would help

 

Yes you can, The cages are dimensionally the same from 69 to 96. One noteable difference in XJS and XJ cages is that the mounting holes for the exhaust pipe hangers are in a different location. Each can be retrofited to work with the other by simply drilling the holes in the right location. There was a stready stream of improvements over the years. There were many minor differences such as hub material thickness and the way the early 70's XJ's oiled the diff side bearings. In 94 the XJS got larger outboard brakes and the convertibles got much larger vented outboard brakes. Even so they will all bolt in to each other. I know becasue I have a 1996 XJS convert cage in 76 XJ coupe, it bolted right in place but I did have to convert it to a single brake fluid channel using a T fitting. At some point unknown to me Jaguar went from 3 channel ABS to 4 Channel ABS.

Front discs and calipers were all the same from 76 to 96 for the xjs and 74 to 87 in the XJ. In the early 80's the kings pings got larger and so did the wheels bearings and the inner grease seal was improved.

 

Note that not all XJS or XJ saloon diffs are the same ratio and many XJ saloon diffs are not limited slip ones, whereas all XJS diff are LS.

Greg