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      04-30-2010, 01:32 PM   #2
epbrown
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Drives: BMW M Coupe, Porsche Boxster S
Join Date: May 2007
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Quote:
Originally Posted by spdracer35 View Post
So, for those of you who have upgraded:

Did you install a new diff, or did you just change the ring and pinion?

If the ring and pinion was changed, outside of things like fluid, did you replace anything else?

Am I completely misunderstanding what is involved with doing this mod? Please enlighten me.
You'll find more experience with this on an M3 forum like, well, www.m3forum.net; it's a pretty common upgrade on the E46 M3, and comparatively rare on the Z4M. Offhand, I can think of 3 posters here that have done it and as far I know both of the otherss have sold their cars.

I did the Dinan swap (3.91:1 gears), where I got a complete diff already rebuilt with the new gears inside. It's more expensive, but faster - took about 4 hours (both times, because the first was bad).

From what I know about the ring and pinion swap, most shops do what Dinan does - they rebuild the diff with the new gears, just as you've been told. The gears should run you $600 or so, a shop will charge $1200-$1500 depending on your market's labor rates. The Dinan swap was $3300 all in, so yeah, the rebuild route is cheaper.

The chief reason for going with the Dinan swap is convenience and, supposedly, Dinan's expertise. I'd say find a competent shop and have it done. Fully half of the Dinan swaps I've heard of require a second install because the first diff wasn't rebuilt properly; mine was replaced after 600 miles. They stood by their work, but doing it twice was a hassle, and one I paid a premium to them to avoid.
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