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)

[Anton CH.]

What transmission do you have mated to your M50?
According to Bentley I have the Getrag S5D 310Z.

Remember that the input flanges are different from autos to manual and they can be tricky to replace. Output flanges should be the same on both.

[DanDombrowski]

I have a 3.73 sitting in my garage waiting to go in, I might get to it this weekend with the transmission, I'll let you know how it turns out.

[pyro]

EDIT: yah sumdude said it, he has my old e34 and the 4.10 is just too steep, it actually has a slower 0-60 time than stock 3.23 because you have to shift more, my shifting probably wasn't up to par but still it gets annoying and then cruising on the freeway is no fun.


for the output flange you need to make a custom socket unless you want to spend something like 70$ for a thinwall 32 i bieleve. What I did to do mine was took a normal cheapy 32 mil I THINK just check the size to make shore, and put it on my impact gun and took it to the grinder, Kind of like a mettel lathe. Worked perfectly and didn't crack.