# M6 Diferential?



## Jrvna (May 10, 2010)

Is it a good idea to swap the Differential on my 84 633csi, for a 85 M6 differential?
I heard it will kill my gas mileage. What is the benefit?


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## ///M Blitz (Oct 27, 2004)

Jrvna said:


> Is it a good idea to swap the Differential on my 84 633csi, for a 85 M6 differential?
> I heard it will kill my gas mileage. What is the benefit?


The 85 M6 has a higher (3:71) final drive ratio, which will negatively affect your highway mileage, because the car will be reving higher; however, your city mileage should improve, although not enough to offset it.

The main benefit will be better acceleration (although your top speed will decrease). Also, the M6 has a limited slip diff, and I think your 633 has an open diff (not sure about this). If so, you will get better traction.


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