I have a 1997 Jaguar 4lire sovereign and need to either rebuild the diff or replace it with a good silent one, what is the ratio of the 4 litre sovereign long wheelbase 1997 year.

 

Probably 3.58:1
The 3.2 cars are about 4.01
The XJRs are 3.27

You may do well to talk to Simply Performance down in Dorking. http://simplyperformance.com

They do rebuilds and parts as far as I know.

Let us know what you do in the end, good luck

 

Likely 3.58. Options were 3.27 for the XJR, 3.77 for 3.2 automatic and 4.09 for 3.2 manual. V12 cars would have been 3.58.

It's typically the bearings that go noisy, output shaft bearings are prone to failure.

If you don't want to do it yourself, I'd send it to Alan Slawson, he's a Jag diff expert. AJS Engineering Services - Jaguar specialists

 

They are all color coded for the ratio and a BLACK CROSS designates Limited Slip.
(red/yellow stripe=3.58:1)

Look for the sticker on the rear cover.

bob