How do I ID my Diff?

[M3KUK]

Hi, trying to work out what ratio Diffs my cars have, how can I ID them? 1989 325i Auto Saloon and 1992 320i Auto Convertible.

[maxfield]

There's a tag on the back plate of the diff.

[Doobit]

If you look at the rear of the diff, you should see a metal strip (tag) bolted to the diff. This will have the diff I'd and ratio stamped onto it.

[M3KUK]

OK thanks.

[M3KUK]

It says 3.73 - 586. 3.73 Ratio then? What about the 586?