Diffs

[hampton]

my e30 was originally a 1989 320 but had an engine conversion to the 325 engine. the standard 320 diff ratio is way too small so looking to fit one from a 325. what case size will fit and will it improve my ratio problem?

[Duke137]

http://www.e30zone.net/e30zonewiki/inde ... fferential

All the info you need is here mate

[daimlerman]

Your 320i will have a small case 4:1 diff,this gives 65mph at 3000rpm.

Three ratio's were fitted to 325i,all in medium case size;
3:64
3:73
3:91

A 3:64 will give 73mph at 3000rpm.

Small case/medium case?
Small case has 6 bolts holding the rear cover,medium case has 8 bolts.
The case's are a different size in all directions,but any ex E30 diff will just bolt in,the width difference is taken up by differing output flanges,the length difference by sliding the prop shaft at it's centre,splined joint.(just slacken the collar nut and belt the diff end with a large birmingham spanner)

Be aware that E28 was also fitted with medium case diffs,but the output flanges will require E30 types fitting.

When swapping diffs,do not forget to remove the speedo sensor plug!

[hampton]

brilliant, thank you very much!