Change Z4 3.0Si Diff to M LSD - Cost/Parts?

I

Incompatible

Active member
 San Diego
I'm doing my research for options on upgrading my non-LSD diff to a limited slip type for my 2007 3.0Si Coupe. Performance, cost, and maintenance are the main aspects of interest. Car use is primarily for street but will see some autox and track time.

I've looked at the Quaife and performance engineering setups and would like to compare those to the Z4M setup. I realize that the M swap would require additional subframe parts, not sure which. I've read through most of the threads on this topic, but price info is minimal.

Any info / thoughts are appreciated.
 
wouldn't it just be easier to buy a used M for the track? Have you checked what Dinan offers?
 
very very expensive

M differential is different than the regular diff. input output flanges, axle length, whole entire rear suspension. so you would have to get the ENTIRE REAR END from an M

just get aftermarket LSD
 
It has been done, b
but the m's are all about the revs not the diff. I'm pretty sure and correct me if I wrong, the si auto has the 3.64 and the manual
has the 3.46. Both are stout, I know some e46 steps are begining to run 3.91's out of the x3. You can find a lsd unit for cheap on the e46 forums as a lot of guys are parting there cars out. But honestly if you are not a track hound, an lsd in my opin is not neccesary. take the money and drop it into the suspenison and exhaust. The lsd option is valid but costly so ultimately it is up to you. good luck :thumbsup:
 
The M rearend swap has been done by Curtis on this forum. You can check his car at simpson motorsports web page. I had a tread on this forum on that subject make a search for LSD and it should show up.

I believe the cheapest way is to get an LSD from Quafie and a used 3.64. That will be the way I will go in the future. I am sure Curtis will write more in details when he saws the subject.
 
I webpage at Simpsons is kinda outdated now, a lots changed in the two years or so since we put the spec list in there! I do still have the E46 M3 rear axle in there though. It was a complete axle swap I did rather than just the diff. It meant that the whole rear is much tougher than the standard 3.0 unit fitted to the Alpina plus the ratio change helped on the track. The M3 rear assembly bolts straight into the Z4 floorpan however the axle is narrower than the Z unit so you have to use wheel spacers or offset wheels. I fittted M3 front hub assemblies too. Nowadays it's probably easier to fit a Quaife unit as suggested. Drexler make good LSD's too but they tend to be expensive. TMS are worth a look.
 
Curtis said:
I webpage at Simpsons is kinda outdated now, a lots changed in the two years or so since we put the spec list in there! I do still have the E46 M3 rear axle in there though. It was a complete axle swap I did rather than just the diff. It meant that the whole rear is much tougher than the standard 3.0 unit fitted to the Alpina plus the ratio change helped on the track. The M3 rear assembly bolts straight into the Z4 floorpan however the axle is narrower than the Z unit so you have to use wheel spacers or offset wheels. I fittted M3 front hub assemblies too. Nowadays it's probably easier to fit a Quaife unit as suggested. Drexler make good LSD's too but they tend to be expensive. TMS are worth a look.
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Thanks
 
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