New Guy Looking For Help On 1991 318i Rear End

[teamjunk58]

Hi, I'm new. Please go easy on me. I have owned plenty of cars but never a BMW. I now have a 1991 318i that I would like to put an LSD in. It looks pretty easy to swap, I just need to know what I can swap it with. I went through pages and pages on here and all I really found was a thread about how to pull one out with a forklift. Haha. This is not a street car, and it's not really a track car. Let's leave it at that. I just need to know what has an LSD that will work in my car. Or where to find one. And what they're worth so I don't get ripped off. If all else fails, I'll weld the thing together. Just looking for options. Thank you very much in advance.

[B C]

4cyl cars (with the exception of the M3) came with what is known as a "small case" diff.

6cylinder cars came with a "medium case" diff. Replace the word "case" with "penis size" and you get the jist

You will have a better chance of finding a medium case lsd than a small case lsd and you will not only have more variety of ratios, but they will likely cost less.

I have removed and installed an e30 diff no less than 6 times and now it feels like something only slightly more technical than an oil change.

Do you have plans to increase power?

Also welcome to here

[teamjunk58]

Thank you for the welcome wagon sir. I do not plan on touching the engine. It is already pretty nasty for what it is. I don't know what's been done to it but a previous owner liked this car way too much. I am just looking for a better rear end to help with traction. I assume the medium case can only be found in the e30 body style? And is there any kind of rhyme or reason to them? Such as ALL 6 cylinder cars had them. Or ONLY automatics had them. Etc. Etc.

Again, thank you for any and all help.

[CMart]

How hard is it to swap from small case to medium case?

[B C]

The axles are the same, just swap the diff and you are good to go.

Medium case can be found in the e30, and e28 (rear cover needs to be swapped)

[jc43089]

I have a 4.10 and 3.15 both med case but they are both open difs. I recently bought a 3.23 LSD from an e36 M3 for 300ish, not am exact price but I bought several things together. That seems to be an average price for that ratio. I assume yours is a 5 spd?

Sent from my potato phone

[teamjunk58]

Yes, my car is a 5-speed. While reading on line somewhere, it stated that 5-speed cars had open diffs and autos had limited slip. But I don't know if that is accurate. I honestly don't care what the gear ratio is, I just need to get out of the hole and one tire is not cutting it. I just need a cheap solution that will bolt in.

[mkoepp]

Yes, my car is a 5-speed. While reading on line somewhere, it stated that 5-speed cars had open diffs and autos had limited slip. But I don't know if that is accurate. I honestly don't care what the gear ratio is, I just need to get out of the hole and one tire is not cutting it. I just need a cheap solution that will bolt in.

The LSD was an option and available with either transmission. You have to be careful what you read online, not all of it is legit.

[jc43089]

http://www.e30zone.net/e30zonewiki/index.php/Differential

 

Here is some good info.

[CMart]

From your link:

 

 

Does switching from small to medium or medium to small affect your needed driveshaft length? it looks so by the picture.

[B C]

The two-piece driveshaft has a couple inches of length adjustability via loosening the collar nut on the splined connection

[i_love_cars]

i want to make sure OP is talking about the same thing everyone else is:

 

we're talking about an LSD that's already installed to the pumpkin, which indeed is not that hard. 

 

But if you are talking about taking a pumpkin apart and applying an LSD, you better damn sure know what you're doing. There are a myriad of things that can  go wrong if you aren't good and have the right tools. A lot of people don't know how to properly install an LSD and end up with things like backlash being way out of spec. 

 

as long as you're talking about juts swapping in a new pumpkin with an LSD in it, then carry on.

[B C]

Gear setup seems like as much of an art as engine rebuilding

[teamjunk58]

Yes, I am just looking to swap the whole case. I dont know how these carriers differ from a chevy rearend as far as assembly but I'd rather not find out. Haha.should I just post in the parts wanted thread or can any of you guys point me in the right direction?

[mkoepp]

I found this awhile back. Looks like it is not too difficult. 

 

http://www.mye28.com/viewtopic.php?t=93418

 

 

[teamjunk58]

That doesn't seem bad at all. Hopefully I can just find an lsd soon. Would save me a lot of work. Thanks for the info!