Rear Differential Suggestions for an M50

[stilljester]

Looking to swap a new differential into my touring as part of a 5spd conversion. What do you recommend? 3.46? 3.73? 4.10? LSD?
Suggestions Anyone?

[bimmerd00d]

3.23 is stock, and that's rather high for my tastes. I always felt like it needed a 6th gear for the highway. 3.46 would be about the highest i'd put behind an M50.

[Anton CH.]

I just did an upgrade from 3.23 open end -> 3.46 LSD (40% lock) last weekend. The diff is aftermarket so it has higher locking percantage and uses 3 clutches instead of 2.
The 3.46 improves overall torque marginally. I wouldn't consider it an upgrade but ithe extra torque is noticable around town. It is most noticable around 75 mph because it puts the RPMS right into the peak torque range. If you do a lot of high speed cruising just be aware aware that your engine is going to be high. Right now its about 3200@70mph from 3000@70. There is no way I would put a 4.10 in this car.

[GoldenOne]

what about a 3.91?

[John B.]

I've been wondering the same thing as I want to round up the pieces to swap out the auto in the 95 Touring we just bought when the auto goes south if not sooner. I take it the gearing in the M50 5 speed is lower then in my 535i 5 speed?? The 3.46lsd works really nice in the 535i on the highway.

[BillionPa]

3200 at 70!? damn thats high, im a hair under 2000..... which in my mind is too low. it does indeed sound like a 6th gear is appropriate for the M50.

[Anton CH.]

3200 at 70!? damn thats high, im a hair under 2000..... which in my mind is too low. it does indeed sound like a 6th gear is appropriate for the M50.

You don't want to know what it is at 80. But I think that is just due to the 5spd gearbox as well. My friend w/ a 94 525 auto has his RPMS in the 2k range at 70. So go figure.

[stilljester]

Right now its about 3200@70mph from 3000@70. There is no way I would put a 4.10 in this car.

What transmission do you have mated to your M50?

[ILoveMPower]

3.46 M30 5spd = 3k rpms @ 80mph

[SumDude]

4.10 lsd at 80mph = 5K
I have a 4.10 lsd and I like it around town but is really bad on the freeway. It killed my fuel economy highway so I plan to put the stock diff back in around summer time. (too cold outside)