bmw e30 diffs

[waddic 1]

hi there i am wondereing if the auto and manual diffs are different and will it make much of a difference if it is?

also does it amtter also if its 320 or 325 as well

[_ethrty-Andy_ 2136]

yes. ratios are all different. but they are all interchangable

[waddic 1]

a mate is after a diff and his car is manual and oi ahve got a couple of auto diffs. will it make much of a difference? are the manual ones much more expenxsive?

[hotwire 352]

Depends - there are variations between models

325's have a medium case where 320's are small - can interchange the two with doing halfshafts as well

Ratios- Generally autos - 4.1(318) or 4.45 (320 facelift)

Pre F/L 320 autos can be 3.7ish

Manual 320's 3.6ish

There are heaps of variations

[Silver Fox 43]

Small case and med case are interchangeable without having to change the driveshafts, any ratio diff, small or med case will fit any E30.

[waddic 1]

so really its a no then, the guy would come back to me about it

[bmpower 3]

Small case and med case are interchangeable without having to change the driveshafts, any ratio diff, small or med case will fit any E30.

Whilst you don't have to change the shafts - aren't the 325 shafts thicker than the 320/318 ones?

[Silver Fox 43]

Not needed for any standard E30, 325 or otherwise, I haven't seen any of the race cars screw shafts yet.

[gouba 0]

Are they actually the same? ism't a medium case diff slightly longer than a small case (but same width?)

[_ethrty-Andy_ 2136]

Are the driveshafts really different too? i thought it was just the axels that were thicker?

OP, if you dont already know how to find out what ratios you have, take a look at the back of them and you should see a metal tag attached to ond of the bolts. clean/degrease/wriebrush etc that till you can see the numbers on it and the first three or the last three (cant remember off the top of my head, should be obvious though) tell you want ratio it is.

[gouba 0]

It shouldnt be too much of an issue with the axles being slightly thicker, I cant imagine it would be easy to break the things.

Im suprized the larger medium case diff physically bolts in to the same space as a small case diff

[Silver Fox 43]

Exactly the same dims from side plate to side plate, and the mounting points. They are a straight swap.

[pureboiracer 0]

med case diffs are slightly longer but this can be taken up in the slip joint of the driveshaft.

[gouba 0]

med case diffs are slightly longer but this can be taken up in the slip joint of the driveshaft.

Ah sweet, I was wondering about that.

Will make my swap much easier then