differential question

[R&D man]

I have a 86 325es and Iam currently collecting parts for the m50swap
The car is an automatic and I will be installing the 260 tranny...question is will my current differential work in this case.

[lennon]

yes it will work, but you'll probably want a shorter gear ratio differential to better match the rpm range of the m50.

[Wh33lhop]

You've got a 2.93, you'll probably want a 3.73. I wish I had a 3.46 in my M50/G260 car, it revs a bit high on the freeway.

[Fusion]

Btw: how long did it take to you swap the diff first time, how long after knowing exactly what to do?

[Wh33lhop]

Btw: how long did it take to you swap the diff first time, how long after knowing exactly what to do?

Took me quite awhile. Those diff-to-subframe bolts refused to budge, so I actually had to take multiple trips to the hardware store to buy cheater bars (lead pipes) of appropriate length and diameter. I wound up finishing at 2AM, although I started pretty late:



Having the tools and knowledge (and looser diff bolts) that I do now, I could probably do it in 2-3 hours. I just tried the bolts about 17 different ways before breaking down and asking a friend for a ride to the store.

[lennon]

The first time I ever swapped a diff on an e30, it took me all day. Not every minute was spent working, but most of the time was. It wasn't my first differential removal in a car either. I had quite a problem getting one of the diff to subframe bolts out. The rear 2 of them are a little hard to access anyway. I bought a nice wrench to help me out, but there was no way to get any of my breaker bars on it. I live in Florida and my car is very rust/corrosion free, so I imagine those bolts could be a lot harder to get off in different regions.

I've done diff swaps in several e30s, including that same car again, since that time and they've all gone smoother because I already have the technique down and proper wrench for the job. It'll need to be one like this: http://www.gearwrench.com/catalog/wr...tric&part=9919

Of course it doesn't have to be flexible or ratcheting, the one I have is like a fixed 45 degree bend at the box end. Get under there first and check it out so you don't waste time going to buy a wrench in the middle of the job. Its not worth trying to do it with a straight wrench or anything else. Start hitting the bolts with rust penetrating oil a few days or more in advance.

Good luck, and I would recommend a 3.73:1 ratio with the m50 and g260. It suits the motor well and is easy to find. Wheelhop's probably right about a 3.46 or so possibly being better for some people. It's all personal preference. I have an s50 e30 and I actually drove it for months with a 3.25:1 just because that's what I had in it before. It wasn't slow. Now I have a 3.73, but really I'd like to switch to the ZF320 transmission and try some appropriate ratios for that. That'll probably never happen though.


edit- wheelhop, is your car cosmosblau? im sure it says in your swap thread or something but im too lazy to look

[Wh33lhop]

I did it with an open ended wrench. :p

The car is Cirrus. Love that color, wish the paint weren't peeling off the roof.

With the M50 the 3.73 is a very fun diff, fist and second are pretty short and third will take you to 93 or so at 7k. But it's still turning over 3300rpm at 80, which was ok for the M20 but I think it's a bit much for an M50. I'd rather cruise at 3000 or 2800 at 80. But a 3.73 is certainly a lot easier to find than a 3.46, and it's a bit more short/fun, so why not.

[Fusion]

Thanks guys. Good info.

[lennon]

I did it with an open ended wrench. :p

The car is Cirrus. Love that color, wish the paint weren't peeling off the roof.

With the M50 the 3.73 is a very fun diff, fist and second are pretty short and third will take you to 93 or so at 7k. But it's still turning over 3300rpm at 80, which was ok for the M20 but I think it's a bit much for an M50. I'd rather cruise at 3000 or 2800 at 80. But a 3.73 is certainly a lot easier to find than a 3.46, and it's a bit more short/fun, so why not.

Damn you! I couldn't get the ones that I had back then on it. I remember deciding the kinked wrench was necessary. On my old eta I was turning 3000+ on the highway going 75-80. And yeah, nice color. I have a cosmos and I just haven't seen many others. In that picture yours looks the same color as mine.