1990 XJS rear end compatibility
 

Im currently doing a 350 swap. Already removed v12 engine and trans and bought donar car 1994 firebird lt1/t56 and have removed engine and trans. I have a 1990 xjs with a 2.88 rear end. I would like a list of all the jaguars with posi 3.54 rear ends that can bolt up to my jag? I heard it normally has to be a straight 6. So could some one list year and model for rear ends. Im new to blogs and no mechanic so please play nice i know some of you guys can be savages if some says something stupid. Appreciate the help.

You can technically use all Series 1-3 XJ rear ends as well as the E-Type, Mark X, 420G etc.

As you state, the 6 cylinder models mainly had the 3.54 ratio.

Avoid anything before the E-Type (different axle) as well as after the Serie III XJ/XJS... They have the newer XJ40 style set up with a different differential. And of course everything after the XJS/XJ Series III... They all used a modified rear axle with a different differential as such.

Any Jaguar IRS rear end gears will fit the XJS. Mine has 3.58 from an XJ40.

There are 2 ways to tackle this.
1. Machine a spacer and use the 2.88 centre.
2. Find a complete LSD with correct gears. The centres are interchangeable.

The 4.2L S3 XJ6 came with 3.07
XJS 6's had 3.54
XJ40 2.8L had 3.54 IIRC.

Look for the smaller 6 cylinders, they won't have LSD.

The IRS diff looks totally different on the XJ40 aka X300 aka X308!? Can they really that easily be interchanged or do you mean the insides?

The centre is interchangeable. I have the diff mounted Speedo so I had the centre hybrid, it's part XJ40 and part XJS.

The XJ40 drive shafts and outboard brake hubs can be fitted as well, all you need to do is bush the XJS LCA

Oh, so the internals are interchangable... If the TE wants a plug and play, then that would be more so as I noted...