Z4m vs e46 M3 LSD (differences) ?

[DONDP]

Alright peeps,

I have been going about a differential upgrade and acquired a genuine BMW Motorsport 4.10 pinion and crown set. I thought the easiest way would be to acquire another diff and get it rebuilt with the new gears.

I was under the impression that the e46 M3 and Z4m diff were the same except for the rear cooling fins which you can swap over. On initial inspection this would seem correct as the front pumpkin part of the case is identical however upon swapping the rear part of the case, the internals are somewhat different. Here are some pics:








I have had a hunt around and both are genuine variable m differentials and apparently there are 2 different types. The question is what are the differences??

For reference The Z4 one is the blacker one and the clean one is the M3.

[ga41]

Genuinely at a loss! Thought they were the same as well!

[DONDP]

I wonder if the z4m is closer to the e90 M3 internals, but I cant find a picture or even a description of the differences between e46 and e90 diffs...

[ga41]

According to RealOEM.com they have different parts numbers as well although it doesn't mention the actual differences.

E46 M3: http://realoem.com/bmw/showparts.do?mod ... g=33&fg=05

Z4M: http://realoem.com/bmw/showparts.do?mod ... g=33&fg=05

BMWFans.info has slightly more information. They say that Z4M diff part number 33107838 954 was used until May 2007 then was replaced with 33107840534, both those are different than the E46 which is 33102282481. http://bmwfans.info/parts/catalog/E86/C ... ve_output/

Hope you get to the bottom of this as it's something that could be of use to others as well.

[DONDP]

Now that is interesting, especially since my z4 is a 2006 car so should have the earlier diff.

I did find some info on zpost but they put the different part numbers down to the rear of the diff casing being different. I feel a friendly phone call to birds coming along...

[ga41]

Thinking about it a bit more, it could be just different manufacturers but at same specifications. It's not unheard of for car companies to change Original Equipment Manufacturers during the life of a car without changing the specifications of the particular part, could've been done for cost reasons for example. Since they both are 3.62 they should work the same even though they might look a bit different.

[DONDP]

Thats not a bad shout, all my reading so far has said that all m differentials use the same shear pump setup and that all offer full variable locking all the way up to 100% So that may well be the case. There were different internal diameters for different m cars but the e46 m3, z4m and e90 m3 all have the 210 diameter irrc.

Its going on the car anyway now, my rationale being that if it worked fine on an m3 with the same engine as the z4 it should work fine. Considering its freshly rebuilt it may just work better than the old one anyway.

Looking forward to the test drive now but thats not till Monday...

[ga41]

Don't forget to give us an update with your impressions!

[exdos]

If the diff physically fits it will work fine. I fitted a 3.46 diff from an E28 to my Z3MC with an OEM 3.15 diff. The only problem was the 3.46 diff had a slight whine even after a rebuild.

The 4.10 diff will sharpen up your MC

[goon]

I know I just had new glasses but are they different in size?

[DONDP]

The diff casing is exactly the same so will fit perfectly, its just the internal LSD part that is different. Its dimensions are different but as far as my research shows it functions in the same way. Which is why GA41's idea makes sense about bmw swapping manufacturers.

The m3 and csl boys rave about the 4.10 final drive so should really sharpen the MC up. I will definitely keep you all posted and share the results.

[DONDP]

Hi chaps,

Picked the car up last night and first impressions are good, in fact better than good. 2nd gear is a real whack in the back and 3rd gear just gets eaten up as the speedo climbs to license loosing speeds whilst I sit there with a childish grin on my face.

Still need to drive it a bit more to give a full appraisal but I have a feeling this will be on my highly recommended list second to the AP brakes...

[ChawenHalo]

different wheel base and width = different diff.

I know that Quaife have various options on each BMW diff but which also vary from model to model.

[DONDP]

different wheel base and width = different diff.

I know that Quaife have various options on each BMW diff but which also vary from model to model.

Hmm not sure about that. The e46 m3 and e46 m3 csl have different rear track widths but still run the same differential... Pretty sure also that the Quaife differential is the same for the e46 m3, e46 m3 csl and z4m.

The differential casing between the e46 and z4 is exactly the same its just the internal component that differs. The only conclusion I can come to is that the z4 was built after the e46 stopped production so BMW probably swapped oem manufacturers inline with the ones that were chosen for the e90.

Either way the new one in mine is working far better than the old one, I really didn't notice the degradation in the old one but this new one is far more sharp and predictable.

[aerobod]

different wheel base and width = different diff.

The diff casing and drive shafts are the same on the Z4M and E46 M3, the slight difference in track width is due to lower offset wheels on the M3.