Also the Xj40/X300 hemisphere will fit in the XJS housing. I know this for sure as mine has 3.58 LSD centre from an XJ40

 

Are the axle splines the same as the older shafts? Do you have the diff mounted speedo, and use that pickup on the later center section?

 

Yes and Yes.

The splines are the same. The pinion snout was longer and had to be machined down that's all. The other thing I would have done is tighten up the XJ40 LSD as it's not as tight as the XJS one.

I hybrid the diff centre. So mine uses the original XJS outer ring for the speedo

 

Hmm, never thought of using an XJ40 section. There is a 93 Sovereign at the junkyard near me, I wonder if it has LSD? Probably not.

 

If funds are no object Quaife make a torsen centre for the Jaguar diff, but these run at around $1500.

Something like this would do being an XJR i would expect it to have an LSD I think the V8 XJR used a tall diff 2.87 due to the low 1st in the Mercedes 722.6 trans.

JAGUAR XJR 1998 1999 2000 2001 2002 2003 REAR DIFFERENTIAL | eBay

 

Alas, money is an issue right now. As far as I know, none of the US/Canadian spec X308's had limited slip, and of the X300's only XJR's had it. I'm not sure about a Canadian market XJ40, that's what I'd be looking at. Considering it is snowing tonight I'm not really thinking about a junkyard trip tomorrow to find out!

 

After doing much work, which included a full diff and IRS rebuild, the car is finished and back on the road. I certainly learned more about diffs than I ever wanted to!

In this case, I took an 86 Sovereign and used it's case, as it was much heavier and thicker walled than my 94. I used the side gears out of it, and could have used the cross shafts. It was 2.88 ratio, so the carrier was different and not compatible with my 3.54 crown and pinion gears.

I also took the diff out of a 1987 XJ40. Canadian spec cars had 3.54 locking on the early XJ40. Unlike later XJ40 and X300, the pinion has an adapter to provide the centre locating pin for the drive shaft, so the gears were the same as the XJS. The limited slip was similar, but different, so I didn't use it. I could have swapped it all as an assembly, but the housing was slightly bigger than the XJS, so I couldn't use the speedometer gear. The internal gears and clutches of the limited slip are different to the earlier XJS/Series III cars.

The axle is nice and quiet now, and the car isn't squirrelly in the wet and doing turns, so I'm happy! Previously it felt like an early 911, very tail happy.