Z4M Gearbox

[Mangozac]

A mate of mine here in Australia broke the gearbox in his Z4M 18 months ago. He's been searching for a replacement ever since but as there are such a small number of of Z4Ms here he's had no luck. The box is a GS6-37BZ-TJEE

He tried to get it repaired but in the process the rear case shattered and log story short we no longer have even the broken gearbox.

We found a GS6-37BZ-TJES from a 2006 E87 130i and from doing some cross referencing on realoem most of it checks out. Output flange is the same too. The only unknown is the input shaft - the guy selling the gearbox doesn't think it will work. The Z4M has a model specific clutch plate, but it may just be because it's a larger diameter than the usual clutch plate used on the S6-37. On most other BMW engines of that era the input shaft bearing is incorporated into the flywheel but on the S54 this bearing is in the end of the crankshaft.

I've found a discussion where a guy retrofitted an E46 330i transmission (GS6-37BZ-THEB) to an E46 M3 (I don't know why he didn't just modify his SMG box to manual?!) and he claims he needed a different clutch, flywheel and starter! That gearbox has two letters different in the variant code though, so it may be much more different.

So I thought I'd post here in the long shot that perhaps somebody knew more about this than we do. If we still had the original gearbox it would be an easy process to just put them side by side and compare...

Alternatively, does anybody have a spare Z4M box laying around they would ship to Australia?

 

[ga41]

Can't help you mate I'm afraid but hopefully you and your mate get some answers soon

 

[Mangozac]

Cheers mate. Further research has confirmed that the gearbox input shaft will be the wrong length on the other variants. The S54 simply has a fairly unique arrangement (among BMW engines) with the pilot bearing incorporated into the camshaft crankshaft instead of the flywheel.

Theoretically it should be possible to swap over to a different flywheel (we've been told an M54 one might work but have not confirmed this) and matching clutch plate but we really need a shop experienced with engine swaps and Frankenstein jobs like this to sort it out...

 

[Mister T]

Can't you just pull the 130 gearbox apart and use an E46 M3 input staft?

 

[Mangozac]

Apparently not. My understanding is that they can only be opened and closed with the special tooling at the factory, otherwise the case is likely to shatter.

 

[Vanne]

really? you dont think that sounds a little like cods-wallop? (think thats how you guys say it) :wink:

my mate in Abudhabi has a spare box lying around, but it had issues as he replaced it with a new one. I could ask him what the drama is with it, but id imagine shipping from dxb/abu is going to be a fricking night mare to brissy. might be a good time to replace the original with a 5 speed e46 M3 one.

 

[GuidoK]

with the pilot bearing incorporated into the camshaft I stead of the flywheel.

Am I the only one who doesn't understand this? :idunno:

I have no experience with this but I wonder why a 6 speed from the normal z4 3.0i wouldnt fit. I imagine when the starter sits in a different place (or mounting bolts are in a different place), its just a matter of swapping over the bell housings.
This is purely speculative (no hands on experience)

Regarding reports needing a different cluch: bmw swapped over to a different splined inputshaft when they went from 5 speed boxes to 6 speeds. There may be some 6 speed boxes with 9 spline input shafts for the transitional period (or 5speed with 22), I dont know.

 

[Z4M-2006]

I’m sure he means crankshaft


E46 M3 gearbox no good?

 

[GuidoK]

I’m sure he means crankshaft

Right, makes sense.
But both the z4m and z4 use the exact same pilot bearing.
So I wonder if the input shafts of those gearboxes are indeed different.

Then again, if it fits (in the sense that it bolts back together again) and some dimension happens to be slightly off and it starts jittering and whatnot under load and it exploads, the carnage will be severe :roll:

 

[Mangozac]

But both the z4m and z4 use the exact same pilot bearing.

Yes, the pilot bearings are the same, but the location is different, hence the Z4M requires a longer input shaft.

And thanks Z4M-2006, I did indeed mean to say crankshaft

 

[Mangozac]

really? you dont think that sounds a little like cods-wallop? (think thats how you guys say it) :wink:

my mate in Abudhabi has a spare box lying around, but it had issues as he replaced it with a new one. I could ask him what the drama is with it, but id imagine shipping from dxb/abu is going to be a fricking night mare to brissy. might be a good time to replace the original with a 5 speed e46 M3 one.

I've heard that from more than one source, and given the original box from the car shattered when the transmission shop tried to open it up I'm inclined to believe it. Either way, nobody wants to touch them and ZF will give no technical advice regarding repair.

The gearbox-less car in in Melbourne bit probably not a lot of difference in cost to ship here. Still, depending on what's failed it could still be worth discussing with your mate.

If only we could replace with the E46 box - the reason BMW didn't use it in the first place is apparently because it doesn't fit in the transmission tunnel of the Z4 chassis. I have come across a forum post somewhere of someone refuting that but never saw any evidence to back up their statement that the E46 box would fit...

 

[Z4M-2006]

I "think" when splitting the gearbox casings,they need to be heated, or a heat plate used?

There is a resin if i remember correctly,that needs to melt to let everything come apart.

Although i could be talking codswallop myself here,its a bit of a distant memory

 

[Vanne]

Have a read of this. Zf 5 speed.

https://www.zpost.com/forums/showthread.php?t=1451764&page=7

This guy is a pretty darn handy, so I bet a bit of furbing is required.

 

[Mangozac]

I "think" when splitting the gearbox casings,they need to be heated, or a heat plate used?

That sounds plausible, resin or not. It could be an interference fit.

https://www.zpost.com/forums/showthread.php?t=1451764&page=7

Whoa. Just whoa

 

[GuidoK]

. Either way, nobody wants to touch them and ZF will give no technical advice regarding repair.

But if you have a broken z4m gearbox, and the input shaft is different, isnt it an option to experiment on a 330i/z4 3.0i gearbox and try to put the z4m input shaft into the 330i/z4 3.0i box? Those boxes are usually cheap (I dont know how much that 1 series box is) and easy to come by and my guess is that the internals are the same. It's the same torque designation, same size and same ratio's afaik. (and the original box is scrap anyways).

It would be very interesting to see pictures of that.
Lot of work though but thats why they call it a hobby

 

[Mangozac]

But if you have a broken z4m gearbox, and the input shaft is different, isnt it an option to experiment on a 330i/z4 3.0i gearbox and try to put the z4m input shaft into the 330i/z4 3.0i box?

If we still had any of the Z4M gearbox bits we would give it a go but somewhere along the line someone has disposed of them so now we've got nothing to test with.

Indeed the internals/ratios are identical and if the car was near me we'd bring it and a non-Z4M ZF 6 speed in and work it out but it's interstate