I have a 2000xj8 with 260k miles and a front pinion bearing failing, very noisy and getting worse ... I decided because of the work involved and expense to set up the rear end aga8n after a bearing replacement to get a different lower mileage 3rd member

I purchased a 1998 XJR positraction t9 install and I am now learning this may be a problem for the computer as a result of this speed change

If I’m correct my XJ8 has a 3.08:1 ratio and the replacement from the XJR is a 3.31:1

The computer may see the difference at the trans output sensor compaired to the abs

If true is there a work around besides a mention Unit f9r and by Ford

Thank you
Christopher
Washington State
chrissuperguy@yahoo.com

Looks like the US models for the XJ8's and XJR's had the same differential. But this should be posted in the x308 forum here: https://www.jaguarforums.com/forum/xj-xj8-xjr-x308-27/

Anyways, if you went with a different gearing, then a method to get around the TCU is to put in different abs tone ring. But I believe you should be good since they're the same differential.