Diff swap

[Kingb]

I am looking for a different ratio diff. I currently have an open 4.10. It is terrible on gas ans am wanting to change. I can use a diff out of just about any BMW just having to change out the rear cover correct? OR are there only certain ones. I have a big variety of BMW's just have to check the ratio tab. I doubt any of these have a LSD either.
Here are some of the cars at the junk yard that are 5 spd. The 5 and 7 series are early 90's
735i
730i
525i
520i
325i e30
325i e36
320i e36
318is this has a 4.10 open already checked
318i

[g22]

I'm not sure about the others but the us version of the 325i came with a 3.73 straight swap. e28 fives will swap with a cover change.

[E30_fiend]

Correction, the e28 diff will swap over with the cover swap and swapping the output flanges. They differ from the E30. They won't correctly mount up to the E30 drive axels.

And to the OP, if you have seen a 5 speed E30 325i then that has the 3.73 which you may want. No its not lsd but its still a better ratio for freeway driving. Actually it wouldn't hurt checking the 325i out to see if it has lsd. I have seen some 325i's with lsd from the factory before. It was a factory option when these cars were new. Doubtful but it wouldn't hurt to look.

The other cars you mentioned have odd ratios. The old 7 series has a 3.46 or 3.64 open diff which probably would suit your car very well.

Stick with the E30 fitment. They have a few good ratios to choose from you just have to be patient and look.




Taylor

[Curtis325is]

I think my 4.10 gets better mileage in the city then my 3.73 did. Probably due to the fact that less gas is required to get the car moving (which is where you burn most of your fuel).

[Kingb]

Mine was a 320i now with a 2.5L. It has a 4.10 and so have all the other e30's I ahve checked from the junk yard. I can't even find anything other than 4.10 thats why I am asking what the compatability is.

[alpinaclone]

Mine was a 320i now with a 2.5L. It has a 4.10 and so have all the other e30's I ahve checked from the junk yard. I can't even find anything other than 4.10 thats why I am asking what the compatability is.

Hah, I built one of those when I lived in Germany. I loved it with the 4.10. It ripped on acceleration, and bumping the r3vlimiter it would do almost 140mph.
320s had the small case diff, but it is interchangeable with the medium case diffs from 325s, 323s and as previously stated, e28s.

The car wouldn't happen to be a shadow line delfingrau '86 with headers and a full exhaust would it? I really doubt that that car is still alive.