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Old 03-21-2013, 06:57 AM
nsogiba nsogiba is offline
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Location: Buffalo NY
Join Date: Aug 2011
Posts: 654
Mein Auto: 2001 540i/6
The E46 M3 ring and pinion (3.62 ratio) are definitely compatible with the M5 diff. However, I don't know if the internals of the M5 diff are compatible with the 540i diff, which means the M3 3.62 may not be compatible with your 540i diff.

If I were you I'd buy a stock E39 3.15 out of an auto car as it is a direct bolt in. Before I took my car off the road for the LQ4, I swapped in one of those to replace my OEM 2.81 and enjoyed the better acceleration; highway cruising was only slightly more annoying (higher revs), but above 80mph the engine was really screaming. I would do it again.

If you really have time and money to burn, buy a used E46 M3 ring and pinion and see if it's compatible with the 210mm M3 housing. I probably wouldn't run that combo on the street though-too many revs while cruising on the highway.
6.0L LSx/T56 Swap

2001 BMW 540i/6 Sport, under the knife
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