Diff' compatibility between models? - BMW Forum

325eXTATIC · 05-23-2006, 06:39 PM

Hello all...
My buddy, who is somewhat inept in the ways of forums like this

, is pretty sure he has munged the diff on his '91 318ic. The question he wants confirmation of is "are all the diff's compatible between all e30's? Not talking about just the gearset, but the whole carrier assembly. There are a lot of e30 325 diff's on Ebay, but none of the ones that are local to him mention being compatible with 318's. He's in South Carolina so if any of you are local to him and happen to have a spare functional compatible differential, let me know and I will make sure to pass the word along!

Thanks everyone!

Josh W.

JoeMadoo · 05-23-2006, 07:07 PM

The 6 cylinder E30's and E30 M3's have a large diff, while the 4 cylinder E30s have a smaller diff.

325eXTATIC · 05-23-2006, 07:13 PM

but is there any problem with installing one in the other? Is there a clearance issue or pinion angle change? Would suspension travel cause the larger Diff housing to bottom out under the trunk? Are the suspension mounts the same?

Thanks!

Josh W.

JoeMadoo · 05-23-2006, 07:55 PM

As long as you switch differentials that are the same size there wont be any problems.

325eXTATIC · 05-23-2006, 09:38 PM

I really appreciate your input Joe! The problem my buddy is coming up against is the fact that there just aren't any 318 diff's available for cheap, so he wants to know what challenges he would face if he used a 325 diff. Are there distinct differences in mounting or installation hardware/interface that would prevent him from dropping in a $150 325 diff instead of a $400 318 diff?

Thanks a heap!

Josh W.

JoeMadoo · 05-24-2006, 12:38 AM

I see... I'm not sure if the mounting is the same or not between the different sizes

take a look at this though...
http://cgi.ebay.com/ebaymotors/1991-...spagenameZWDVW

ldsbeaker · 05-24-2006, 10:51 AM

^^ I am teh jealous/hate of you for small bumpers.

draculia · 05-24-2006, 11:03 AM

it should bolt right up. the small diffs have axle flanges that stick out farther to compensate for the narrower housing. everything else should be in the same location as the large diffs.

JoeMadoo · 05-24-2006, 11:51 AM

Haha thanks Idsbeaker, it only takes like 20 minutes to smack them in

davisw999 · 05-24-2006, 12:55 PM

I have an '89 325i. I'd love to put in an LSD. Which models came with compatible ones for this car? 325is & M3?

Thanks!

JoeMadoo · 05-24-2006, 01:39 PM

325e's, i's, and M3's all have large differentials.

325e's have either a 2.79 or 2.91 ratio.

325i's have a 3.73.

325iX's and M3's have a 4.10.

Moosepuck · 05-25-2006, 04:37 PM

http://cgi.ebay.com/ebaymotors/ws/eB...AWNA%3AMT%3A12

Does anyone see a reason that this diff wouldn't fit in my 91 318ic 4 banger?? I'm about to bid..!!

Torque · 05-25-2006, 04:42 PM

Quote:

Originally Posted by Moosepuck

http://cgi.ebay.com/ebaymotors/ws/eB...AWNA%3AMT%3A12

Does anyone see a reason that this diff wouldn't fit in my 91 318ic 4 banger?? I'm about to bid..!!

Did you not read? It's physically bigger than that of a 318 ...

Moosepuck · 05-25-2006, 04:47 PM

Did you read??? Someone also mentioned that the flange width is the same and that it should mount up...

JoeMadoo · 05-25-2006, 09:27 PM

I read!