E46 M3 M-Diff vs E86 Z4M M-Diff ... differences?

[sixspeed]

I was fairly certain that the diff on our Z4Ms was the same item from the E46 M3?

However they have different part numbers as listed by BMW?

Are they interchangeable?

Are there any differences to the casing/mounting/internals?


Basically I'm wondering if you can fit an E46 M3 diff to a Z4M, and vice versa, as a straight-swap, without any modifications?

[onebluemcm]

Is the PN different because of different final drive gear ratios? Can't remember for sure if the ratios are same or different. From the '06 Z4MC my friend had in the Grand Am GS class, I thought the physical characteristics of the diff was identical, direct swap, no mods as you stated... At RealOEM.com, there is one difference - the diff for the Z4M has a $2.16 o-ring at each output shaft that the M3 diff does not appear to have - so maybe there was a slight redesign. That, or I found a glitch in RealOEMs database.... Either way, I don't think this would affect the fitment between the cars - I believe it is still a direct swap...I'd get others opinion because I can't claim 100% certainty...

[Starscream]

The part number is different due to the finned aluminum diff cover beinf different on Z4M models

Otherwise its the exact same diff,

If you were to swap with a E46 M3 you would each keep your finned covers, but the pumpkin part is exactly the same and interchangeable

[sixspeed]

Ah ha! So you can pick up an M3 diff, unbolt the covers, swap, and away you go?

ETA: and is it as simple as I've just made that sound?

[Starscream]

To an extent yes,

I wouldn't call it an easy job, But it depends on your situation,
I personally did my diff with 4.10's on my back with nothing but a set of jack stands holding the arse of the car up,

It would be MUCH easier with a lift

and its also at a funny angle, it doesn't just drop out, it goes in and comes out at an angle and when your on your back lifting it up it can be a bit tricky,
There isn't much room under the Z4M

But obviously it can be done, and a gear ratio swap really wakes the car up

By far my fave mod

[Z4Murder]

anyone by just the ring and pinion from turner? thats what im leaning towards...

[Starscream]

Mine came from Diffs Online when it was near on impossible to find a ring and pinion set anywhere

Heck at one point tischer was selling them!

[epbrown]

Originally Posted by sixspeed

Ah ha! So you can pick up an M3 diff, unbolt the covers, swap, and away you go?

ETA: and is it as simple as I've just made that sound?

There abouts. "Burt Reynolds" on this forum has since sold his car, but he got his 4.10 from an M3 owner that was parting out. They drove to a shop together and exchanged diffs in 2-3 hours.

[polaxgr]

Originally Posted by Starscream

By far my fave mod

why is that? cause u changed it or ... because its way faster and more responsive? now 0-100 is faster ? but lower top speed right?

[Starscream]

Yes it makes a nice difference in acceleration,

When paired with the ESS tune it really makes the car awesome,
Its like they were made for each other lol,

Eventually I'll get around to headers, then the car will be done

[blender]

+1 Diff and Tune make the car really, really fly.

[crfine88]

Originally Posted by Starscream

To an extent yes,

I wouldn't call it an easy job, But it depends on your situation,
I personally did my diff with 4.10's on my back with nothing but a set of jack stands holding the arse of the car up,

It would be MUCH easier with a lift

and its also at a funny angle, it doesn't just drop out, it goes in and comes out at an angle and when your on your back lifting it up it can be a bit tricky,
There isn't much room under the Z4M

But obviously it can be done, and a gear ratio swap really wakes the car up

By far my fave mod

That is awesome!
To me, mods are even more rewarding when you do your own installation.
How long dis this mod take for you?

[DonDP]

Im going to resurrect this one as I have found out some more information...

I started a thread on the UK forum (http://www.z4-forum.com/forum/viewtopic.php?f=9&t=50881) but thought I would share here also:

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.

[psygnosis]

Could part of it be age and parts refinement? What year was the M3 diff from?

[The HACK]

I could have saved you all that trouble...

In the marketing literature for the MZ4 Roadster and coupe, it was mentioned that the viscous coupling in the LSD in the coupe has been redesigned and retuned to provide a rudimentary, beta version of torque vectoring. In any given turn, when both rear wheels are on the ground in full contact and traction, the ///M variable diff is tuned to send MORE POWER to the outside wheel.

An upgrade would be for someone with and E46 M3 to swap to the MZ4 Coupe's diff, not the other way around. The internals of the MZ4's LSD has some basic torque vectoring functions built in.

[DonDP]

Interesting stuff. The diff was from a 2005 e46. I had it completely rebuilt and as I was getting a bizare clunk comming from the rear end which was narrowed down to prop shaft or diff i decided to put it on the car.

I am glad I did, it may be because the old one had 50k on it but this newly built one seems so much more sharp and predictable. Or maybe I am just used to LSDs without torque vectoring... Oh and as the others have said 4.10 diff upgrade, fantastic upgrade.

[ga41]

Originally Posted by The HACK

I could have saved you all that trouble...

In the marketing literature for the MZ4 Roadster and coupe, it was mentioned that the viscous coupling in the LSD in the coupe has been redesigned and retuned to provide a rudimentary, beta version of torque vectoring. In any given turn, when both rear wheels are on the ground in full contact and traction, the ///M variable diff is tuned to send MORE POWER to the outside wheel.

An upgrade would be for someone with and E46 M3 to swap to the MZ4 Coupe's diff, not the other way around. The internals of the MZ4's LSD has some basic torque vectoring functions built in.

Didn't know that! Is that on any literature?

[DonDP]

Originally Posted by ga41

Didn't know that! Is that on any literature?

I have been off googling and haven't found much, but i did find this:

http://www.autoblog.com/2007/12/06/b...ing-rear-axle/

Interesting that the date of the article is Dec 2007 yet my car is a 2006...

[The HACK]

Originally Posted by ga41

Didn't know that! Is that on any literature?

I used to have access to BMW's press site when I had journalistic credentials. I think that's where I found it. Of course, if it's on BMW's press documents it'll likely have been repeated by a few journalist. The only thing I can remember is that the MZ4 Coupe diff is tuned to be more aggressively lock-up prior to sensing impending slip, which is more akin to "1.5" version of an LSD vs true torque vectoring.

[DonDP]

Originally Posted by The HACK

I used to have access to BMW's press site when I had journalistic credentials. I think that's where I found it. Of course, if it's on BMW's press documents it'll likely have been repeated by a few journalist. The only thing I can remember is that the MZ4 Coupe diff is tuned to be more aggressively lock-up prior to sensing impending slip, which is more akin to "1.5" version of an LSD vs true torque vectoring.

Sorry im lost now, i thought the terms 1 way, 1.5 way and 2 way when used for describing an LSD, refered to its behaviour during load, no-load and overun not how quickly it would lock. I was also under the impression torque vectoring would provide yaw control which is a seperate function.

Shame we cant get in contact with Joerg Trommer...

http://www.pistonheads.com/doc.asp?c=104&i=25275

[O-cha]

Originally Posted by The HACK

I could have saved you all that trouble...

In the marketing literature for the MZ4 Roadster and coupe, it was mentioned that the viscous coupling in the LSD in the coupe has been redesigned and retuned to provide a rudimentary, beta version of torque vectoring. In any given turn, when both rear wheels are on the ground in full contact and traction, the ///M variable diff is tuned to send MORE POWER to the outside wheel.

An upgrade would be for someone with and E46 M3 to swap to the MZ4 Coupe's diff, not the other way around. The internals of the MZ4's LSD has some basic torque vectoring functions built in.

There's absolutely no "torque vectoring" in the diff. If you actually read that it was just some marketing team making things up. It cannot be done mechanically with a clutch type without outside input which the diff does not have. A torque biasing diff can sort of do this, but it's not really effective.

Our differentials are hybrids between clutch type and viscous type, and are not in any way biasing diffs. The only thing the viscous pump drive is the lockup that used to be driven by ramp angle.

[O-cha]

Originally Posted by DonDP

Sorry im lost now, i thought the terms 1 way, 1.5 way and 2 way when used for describing an LSD, refered to its behaviour during load, no-load and overun not how quickly it would lock. I was also under the impression torque vectoring would provide yaw control which is a seperate function.

Shame we cant get in contact with Joerg Trommer...

http://www.pistonheads.com/doc.asp?c=104&i=25275

the 1 1.5 2 way is exactly as you said. 1 way only locks on acceleration, 1.5 locks at a much different rate on engine decel, and 2 way generally locks at nearly the same right either way.

How quickly it will lock is called the ramp angle. Look at the center section of the below image, nelow where the yellow is you'll see a diamond shaped hole. That it's diamond shaped means its a 1.5 or 2 way. a 1 way would be a triangle. The angle of that hole determines the ramp angle, or how quickly the diff locks up. The post in that hole is literally transferring the load, and as it pushes on those center housings they are pushed outward. This in turns clamps down on the clutches and locks them together. Steeper the angle the faster that happens.

This action in our diffs is driven by a pump instead of this ramp. The higher the when differential, the more the pump spins, the more clamping force locking the axles. FYI it's very weak and easily overpowered.