850ci Differential opinions

[Jormotors]

Hello, I have a 1997 850ci 5 speed auto and plan on doing a differential swap here shortly. So far I can't decide whether i will go with the Large case 3.15lsd from the e32 750 or go shorter and get a 3.64.

Does anyone out there have a 3.64 on there 5 SPEED 850i? how is it?

I know the 3.15 will be a decent upgrade from the 2.81 so any input would be appreciated.

Thanks.

[dragon850]

3.64 is really fun, not too horrible on the freeway but it depends what you like.
3 15 is not worth it. 3.45 is a happy medium.

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[Jormotors]

Sounds good thanks, i'm thinking of going with a 3.64 open cause they are so much cheaper than the LSD units. 8 series doesn't need to break traction ever...

[Jormotors]

3.64 is really fun, not too horrible on the freeway but it depends what you like.
3 15 is not worth it. 3.45 is a happy medium.

Sent from my SM-G892U using Tapatalk

Do you know what the freeway rpm's are?

[dragon850]

Do you know what the freeway rpm's are?

3.45 is 3k rpm at 80mph, 3.64 is around 3200rpm at 80.
Well it does brake traction with 3.64 but manageable.

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[vwleadfoot]

I have an extra 364 from an E32 if your'e interested. Known good, car got wrecked in the front and has since been stripped. Located in MD.

[vgs]

Do you know what the freeway rpm's are?

This is the ZF 5HP30 (M73 Steptronic) and stock 2.81 differential. The y-axis is engine rpm and the x-axis is speed in km/h.

Gears E31 M73 2.81.png


With 3.15, 3.45, and 3.64 differentials:

Gears E31 M73 3.15.png

Gears E31 M73 3.45.png

Gears E31 M73 3.64.png

I calculated these with my tire size, I am running 255/45R17.

[Jormotors]

Thanks! very good info!

[alex840]

3:15 is perfect. I have it on two cars, one is custom Blaton build and another off of another BMW one of our experts located for me in Bay Area.

Hello, I have a 1997 850ci 5 speed auto and plan on doing a differential swap here shortly. So far I can't decide whether i will go with the Large case 3.15lsd from the e32 750 or go shorter and get a 3.64.

Does anyone out there have a 3.64 on there 5 SPEED 850i? how is it?

I know the 3.15 will be a decent upgrade from the 2.81 so any input would be appreciated.

Thanks.