S6-37 6mt swap info (broken off from junk yard thread)

[terra]

Gotcha, so the Z4M has the longer input shaft as it has to reach the end of the crankshaft and the 330i is shorter since the bearing is on the flywheel. Now I'm curious why BMW wanted to use a specific flywheel for the M3 and Z4M rather than use the clutch assembly and transmission from the 330i in the Z4M.

Yeah it's a fair question. I think it just comes down to *technically* the dual mass flywheel should be relatively matched to the engine's characteristics. And I guess it was cheaper for them to make a few transmissions with a longer input shaft than making and perpetually stocking a Z4M-specific flywheel.

In my mind it should be feasible to build some sort of spacer that sits in the crankshaft and spaces out the pilot bearing to where it should be for the shorter inputshaft while using the S54 flywheel. But the machining would need to be spot on.

[PetrolM3]

In my case it was just a question of what we had lying around, he bought the Z4MR as a lightly hit car that was being parted out, it was sold to us as a rolling shell with no powertrain and we put the car together on a budget with spare parts we had kicking around. I'll get him to report on how the car holds up to aggressive driving, give him a week or 2.

Yes, the Z4M ZF GS6-37 does have a slightly longer input shaft than the 330i variant, the rest of the transmission is 100% identical (minus the shifter but that doesn't matter they can be swapped out for each other).

I will be using the Z4M version of the GS6-37 for my personal E46 M3. It will be mated to the original S54 flywheel and a Z4M clutch kit. I got Ronald to sell me one of his 330i 6MT SSK.

The only part I need to figure out next is the transmission cross brace, as I heard the cross brace for the ZF gearboxes interferes with the stock M3 mid-pipe. I'll see for myself once I'm putting everything together and decide what the best course of action is. Seems like most guys get an exhaust shop to modify the mid-pipe but personally i'd rather cut and well the transmission cross brace itself otherwise it will always be a headache to change exhaust components on the M3.

Thanks for sharing, much appreciated!

There's another forum member on here who was looking to replace his 330i GS6 with a 420G and he was using a customer made cross brace - he recently posted in the classifieds looking to swap his GS6 with a 420G so it should be easy to find him if you want to see what his custom cross brace looks like, I'm sure he'll be happy to share.

[e46IX]

As for the redline shift grind, yes its a real thing even on my own personal low-mileage (50,000 km's) M Coupe. I normally hesitate for a second going from 1st to 2nd on a redline WOT pull otherwise it will grind, can't just slam it into gear. Although to be honest I recently changed the trans mounts out for the Rogue Engineering solid rubber ones and I think there is some improvement there, I may try going to slightly stiffer engine mounts and see if limiting the movement in the drivetrain will help solve that grind.

[e46IX]

Well done!

Has your friend done any aggressive driving yet, shifting at redline? I've read reports of Z4M cars struggling with shifting at redline and that was attributed to the GS6 transmission as this was not an issue with E46 M3 with the 420G. Wondering if the GS6 from a 330i with the shorter input shaft exacerbates this issue even further?

Another question - why did you choose to go with the Z4M clutch kit over the 330i one? Clearly it works and there's a chance it's slightly more capable of handling the S54 power but considering you used the 330i transmission and flywheel, 330i clutch would have been the safest bet which is why I'm wondering how you decided to go with the Z4M clutch assembly? Again, just curiosity in case there's something new to be learned as I love the GS6 transmission and plan to use it if I ever do an S54 swap on my E46 sedan.

Cheers

In my case it was just a question of what we had lying around, he bought the Z4MR as a lightly hit car that was being parted out, it was sold to us as a rolling shell with no powertrain and we put the car together on a budget with spare parts we had kicking around. I'll get him to report on how the car holds up to aggressive driving, give him a week or 2.

Yes, the Z4M ZF GS6-37 does have a slightly longer input shaft than the 330i variant, the rest of the transmission is 100% identical (minus the shifter but that doesn't matter they can be swapped out for each other).

I will be using the Z4M version of the GS6-37 for my personal E46 M3. It will be mated to the original S54 flywheel and a Z4M clutch kit. I got Ronald to sell me one of his 330i 6MT SSK.

The only part I need to figure out next is the transmission cross brace, as I heard the cross brace for the ZF gearboxes interferes with the stock M3 mid-pipe. I'll see for myself once I'm putting everything together and decide what the best course of action is. Seems like most guys get an exhaust shop to modify the mid-pipe but personally i'd rather cut and well the transmission cross brace itself otherwise it will always be a headache to change exhaust components on the M3.

[Slideways]

That’s why he had to use the 330 flywheel with the integrated bearing.

Gotcha, so the Z4M has the longer input shaft as it has to reach the end of the crankshaft and the 330i is shorter since the bearing is on the flywheel. Now I'm curious why BMW wanted to use a specific flywheel for the M3 and Z4M rather than use the clutch assembly and transmission from the 330i in the Z4M.

[terra]

I read that the input shafts have different lengths between the Z4M and 330i gearboxes. Does that not matter since you mixed and matched parts - mainly the location of the pilot bearing?

That’s why he had to use the 330 flywheel with the integrated bearing.

[PetrolM3]

FWIW I just slapped together a Z4M Roadster for a friend, with mix and match used parts.

I used a ZF GS6-37 from an e46 330i, the Z4M shifter attaches directly to it.

I used a flywheel from an e46 330i, and removed the pilot bearing from the S54 (330i flywheels have integrated pilot bearings)

I used the clutch kit from the Z4M, and the starter from the Z4M (same as M3).

Everything works mint, transmission engages and shifts like butter.

I've had both clutch kits next to each other (330i and Z4M. They are virtually identical and all 3 clutch discs (e46 330i, e46 m3, z4m) have a 240mm diameter. There were some minor differences in the pressure plates between 330i and z4m but didn't cause any issues, car drives perfectly normal.

Well done!

Has your friend done any aggressive driving yet, shifting at redline? I've read reports of Z4M cars struggling with shifting at redline and that was attributed to the GS6 transmission as this was not an issue with E46 M3 with the 420G. Wondering if the GS6 from a 330i with the shorter input shaft exacerbates this issue even further?

Another question - why did you choose to go with the Z4M clutch kit over the 330i one? Clearly it works and there's a chance it's slightly more capable of handling the S54 power but considering you used the 330i transmission and flywheel, 330i clutch would have been the safest bet which is why I'm wondering how you decided to go with the Z4M clutch assembly? Again, just curiosity in case there's something new to be learned as I love the GS6 transmission and plan to use it if I ever do an S54 swap on my E46 sedan.

Cheers

[Slideways]

FWIW I just slapped together a Z4M Roadster for a friend, with mix and match used parts.

I used a ZF GS6-37 from an e46 330i, the Z4M shifter attaches directly to it.

I used a flywheel from an e46 330i, and removed the pilot bearing from the S54 (330i flywheels have integrated pilot bearings)

I used the clutch kit from the Z4M, and the starter from the Z4M (same as M3).

Everything works mint, transmission engages and shifts like butter.

I've had both clutch kits next to each other (330i and Z4M. They are virtually identical and all 3 clutch discs (e46 330i, e46 m3, z4m) have a 240mm diameter. There were some minor differences in the pressure plates between 330i and z4m but didn't cause any issues, car drives perfectly normal.

I read that the input shafts have different lengths between the Z4M and 330i gearboxes. Does that not matter since you mixed and matched parts - mainly the location of the pilot bearing?

[terra]

Nice. Yeah that's probably the simplest way to do it. I know there was some concern that the flywheel from a 330 wouldn't be well matched to an S54, but we're talking subtle stuff anyway at that point

[e46IX]

Should be able to get away with the stock driveshaft. Flywheel stuff is a bit of a complication for sure if you're not using the box out of a Z4M

FWIW I just slapped together a Z4M Roadster for a friend, with mix and match used parts.

I used a ZF GS6-37 from an e46 330i, the Z4M shifter attaches directly to it.

I used a flywheel from an e46 330i, and removed the pilot bearing from the S54 (330i flywheels have integrated pilot bearings)

I used the clutch kit from the Z4M, and the starter from the Z4M (same as M3).

Everything works mint, transmission engages and shifts like butter.

I've had both clutch kits next to each other (330i and Z4M. They are virtually identical and all 3 clutch discs (e46 330i, e46 m3, z4m) have a 240mm diameter. There were some minor differences in the pressure plates between 330i and z4m but didn't cause any issues, car drives perfectly normal.

[tnord]

probably the smart thing, I just don't like the idea of spending all of that money and not "upgrading" to a better shifting, serviceable gearbox. I should probably talk to a shop that does SMG -> manual conversions and have them set aside a good unit for me.

[Slideways]

say you had a car with 111k miles, and worn 2nd/3rd synchros that caused gears to grind unless you were very deliberate with your shifts. When it came time to replace a clutch, what would you do?

I'd have a hard time putting my same transmission back in, but I also don't see anything else that's the clear choice. I'm guessing if I could find someone qualified, that rebuilding my existing one would be the most economical.

Reman GS6-37 doesn't seem terribly expensive from the dealerships I'm finding online. It looks like that was the transmission I had in my E90 330, and I could bang through gears way faster than the M3. But potentially having to get a custom driveshaft doesn't sound great, and if you need the flywheel setup also things are getting more complicated and more expensive.

Most cost effective option is the get a good working sub-100k SMG unit and convert it to manual. It is even less when swapping over your manual bellhousing. Also, the shift detent, spring guide pin, and compression spring need to be transferred over to the SMG unit. Big plus is you keep the clutch assembly, driveshaft and shift linkage, so no cost there other than renewing the clutch disc and pressure plate.

Rebuilding service is rather expensive by comparison, like 4-5x, and very few companies can do it.

[tnord]

I have to think finding a used box out of a Z4M is nearly impossible.

the reman units I was finding through dealer websites was about $3k. Add in a flywheel, clutch, and shifter setup and this project follows my rule that modifying anything on this car is about $5k to do it right.

Used units appear to be available for about $1000-$1500, but of course are of unknown condition. Add in a rebuild on those units and you're probably right at the $3k number you can get a reman unit from BMW for.

[terra]

Should be able to get away with the stock driveshaft. Flywheel stuff is a bit of a complication for sure if you're not using the box out of a Z4M

[tnord]

say you had a car with 111k miles, and worn 2nd/3rd synchros that caused gears to grind unless you were very deliberate with your shifts. When it came time to replace a clutch, what would you do?

I'd have a hard time putting my same transmission back in, but I also don't see anything else that's the clear choice. I'm guessing if I could find someone qualified, that rebuilding my existing one would be the most economical.

Reman GS6-37 doesn't seem terribly expensive from the dealerships I'm finding online. It looks like that was the transmission I had in my E90 330, and I could bang through gears way faster than the M3. But potentially having to get a custom driveshaft doesn't sound great, and if you need the flywheel setup also things are getting more complicated and more expensive.