I am wondering if anybody here has swapped a diff from a normally aspirated XJ6 into an XJR. I like the idea of having 3.58 gears instead of 3.27. I am wondering id ABS/Traction control or Transmission control unit will go nuts. If programming needs to be done, I have IDS/VCM setup.

 

I made that swap on my XJR/6. No problems of any kind. Noticeable (but not earth shattering) improvement in acceleration, about 200 rpm higher at 70 mph, loss of about 1 mpg fuel economy at highway speed

I was lucky to find a rebuilt 3.58 diff with limited slip for just $400, including shipping, on Ebay.

Cheers
DD

 

Also I assume you'd have to find an XJ6 differential with limited slip if that matters to you, otherwise aren't the typical XJ6 differentials just an open differential?

I hope my differential never wears out due to cost, but if it does, this is on my list of options to consider. MPG is already awful, so 1 MPG lost wouldn't really matter

 

Yes

Cheers
DD

 

If the LSD unit is still good in the XJR unit, you could
consider swapping it into the XJ6 diff. Or, there is a
Auburn Gear cone type unit that fits.