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Old 02-08-2017, 06:46 PM   #1
Performance Autowerk
Join Date: Dec 2015
Location: Dublin, Ca
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The definitive M5 and M6 differential swap thread

Hey guys.... I was looking for some information a while back regarding swapping a M5/M6 (E60/E63/4) differential into a 550i/650i (or 545/645) and couldn't really find the answer that I was looking for online.

I thought sharing might help out some members in the future.

The answer is YES, you can swap a M5/M6 diff. into the non M-car, but it takes some work.

The differential itself will bolt right in.

The finned cover will cause some clearance issues with the exhaust. In our case we deleted the resonator from the stock exhaust and fab'ed up some pipes to clear the cover.

The axles are the next issue. The M5/M6 axles are a larger diameter at the output flange. No, you cannot swap the flanges as the M5/M6 flanges are substantially different from the stock diff. We sourced some used axles for about $135/ea from an M6. The bearing end is the same. The axles go right in.

Next problem: the driveshaft. The stock shaft is 13/16" (20mm) too long with the new diff in place. One option would be to source a M5/M6 driveshaft, though I'm not sure this would work. Maybe somebody else can confirm. We ended up sending the driveshaft out to have it shortened. Not as easy as it sounds since BMW friction welds their driveshafts together. Our driveshaft shop was able to install Spicer center u-joint to allow for future service and provide the correct length for the rear section. It ended up setting us back almost $500 (there may be a more cost effective option, but we were out of time).

The last piece of the pie... Because the differential is longer, the flange will sit 20mm further forward. The body has a recess above the input flange of the differential. It appears to have plenty of clearance with the longer differential snout, but I assure you that it isn't enough. You need to clearance above the new location of the input flange or it will hit if/when you fully load up the driveshaft/rear axle housing. We used a screw jack under the car and slowly massaged the metal up about 10mm.

That's it...... BMW M5/M6 limited slip goodness in a plain jane 5'er or 6'er. The added benefit of the shorter gear ratio is nice also.

Happy swapping, folks.
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Old 02-08-2017, 06:50 PM   #2
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what a baller

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Old 02-09-2017, 05:36 AM   #3
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There is the pretty common 2.93 LSD from a 325es. How much lower of a gear ratio would you want? The finned cover is cool, but I think it would be easier to tig some bigger fins on the stock cover of a 2.93 then go through all this trouble.
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Old 02-09-2017, 10:07 AM   #4
Performance Autowerk
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Kershaw: This is for a swap into a E63/4 and E60 chassis (5 or 6 series). Lower gear ratio=shorter gears, faster accel.

Anyway, just thought I'd share since these M5/6 LSD's are cheap and there are a fair number of 5/6 series cars out there that could benefit from a LSD. I know I've been fairly disappointed that BMW stopped the LSD train at the E39 chassis.
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