1995 M3 (3.15 vs 3.73 diff) [Archive] - Bimmerfest - BMW Forums

: 1995 M3 (3.15 vs 3.73 diff)

07-17-2005, 08:47 PM
My son bought a highly modified M3 this spring.
It had software, injectors, exhaust, intake, suspension and more upgrades done to the car.
The car runs very well for a 1995 M3.
I was shocked to find out that it had a 3.15 diff.

I own a 2001 M Coupe with the E46 M3 S54 engine.
The 2001 & 2002 M Coupes came with a 3.15 diff.
I replaced the stock 3.15 installed a 3.73 diff, which really tranformed the car.
I believe my 3.73 diff came from a 1987 325is.

Can a 3.73 diff be installed into the 1995 M3?
Does anyone have any experience in this area?
Any recommendations or comments?


07-20-2005, 08:51 AM
The 3.73 diff you put in the MZ3 was out of an E30 325is. Easy swap. AFAIK the E36 uses a different diff.

The 96 and later E36 M3s came with a 3.23 diff, same ratio as the 2000 and earlier MZ3s did.

Autos came with 3.38s, but they are rather expensive, since they are the only other ratio that can be used in a Street Prepared autocross E36 M3. I am looking for one.

But just about any ratio is available for a price. :)

07-30-2005, 12:57 AM
I suggest a 3.38.

08-01-2005, 06:11 AM
If I were to do it again, I would have gotten a 3.46 40% lockup form Dan at Diffsonline.com. I got a 3.38 and it is fine, but the few extrra revs on the highway wouldn't have been a big deal. Plus it comes with a warranty.

RPM's at 80 MPH are 3700 with the 3.38 and would be 3800 with the 3.46.

08-03-2005, 05:31 AM
I agree, if you aren't limited by rules, the 3.46 is a better idea.

08-04-2005, 06:13 PM
Last year I replaced my 3.15 with a 3.23. My original dif just gave out. I bought my 95 from a friend who had made almost all the modifications you can do without going into the engine. The prior owner took it out on the track one weekend and his comment was "I don't remember this car having this much torque". The difference is noticable and yet still suitable for the street. 3500 rpm at 80 mph. I really like it but I will be installing a new ratio when my M3 gets turned into a track only car. It currently has 200k miles and is running as strong as ever.

08-08-2005, 01:29 PM
HOW much does this mod cost?
i might replace mine on my 95 to get the car more lively.

Please advise.
and price etc.


08-08-2005, 05:43 PM
There is a 3.38 for sale on Bimmerforums right now for $650, A newly rebuilt 3.46 with 40% lockup with warranty is about $1600 with exchange.

08-09-2005, 07:03 AM
what does the number represent?
is the bigger the number the more low end torque?
need some education here.


08-09-2005, 11:32 AM
Yes, the bigger the number the more torque you feel. The torque of the engine doesn't change but the torque at the rear wheels does go up. It's all about gear ratios.

The up side is it's one of the cheapest ways to get more torque to the rear wheels.

The down side is that it increases the RPM,s at any given speed.

So, don't over do it. Small steps make a big difference. 3.15 to 3.38 is as far as I would go unless all I wanted is acceleration.

I purchased my dif on ebay for about $400 and did the job myself. I like working on E36's, and in fact, that's my therapy.

Dynamic Entry
02-06-2015, 07:40 PM
Is there a reliable way to identify a rear diff by numbers on the housing?

I pulled the driveline out of an early e34 525 (M50 motor) but the transmission is a ZF 310z which also came on the 95 M3.

So now I am wondering exactly what rear diff I have got here.



03-19-2015, 07:53 AM
Is there a reliable way to identify a rear diff by numbers on the housing?

In the pic, on the bottom left bolt you will see a TAG with the gear ratio stamped on it.
*S* tag on the diff means its a Limited Slip Diff... no *S* means its a "open" diff.
example S3,23 would be LSD 3.23 ratio