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

[Obioban]

Looks like the Z4M used a different clutch and flywheel than the 330i, but I think the same trans. Thoughts on the Z4M parts?

Edit: Z4M used the same flywheel as M3. Am I wrong in thinking that the Z4M used the same 6mt as the later e46 non Ms?

[Obioban]

Shifter and crossmember are different re: 420g vs ZF320 as well as the driveshaft length.

The S6-37 uses a pilot bearing that is inside the flywheel vs inside the crankshaft for the 420g.

Any idea what would be involved in installing a S6-37 into an M3? As in...

Would it need a different driveshaft length? If so, any chance you know what it is?

Shift-- what is different, exactly?

Cross member looks quite different, and has an addition bracket (2 on the diagram). What's the extra bracket do? Does the cross member install in the M3 without any changes?

I suspect a CF driveshaft is in my future, and I already want to change my shifter setup to a 0% reduction AS kit, AND my flywheel is still original at nearly 170,000 miles... so if I was ever going to do this... now might be the time (get it made to length for this swap and get shifter parts that are friendly to the swap).

[George Hill]

Really just need to change the clutch disc with a 5 speed swap.

The ZF 6 speed has a different spline count than the 420g…I think. That’s the downside - clutch choices will be very limited. You can use…gulp…UUC.

I ran a ZF 6 speed with a twin screw kit in my 330 - 345whp and 300 ft/lbs. Never had a clutch or transmission issue. I’d be ok with an S54 and bolt on mods. Might be an issue with a lot of boost.

Shifter and crossmember are different re: 420g vs ZF320 as well as the driveshaft length.

The S6-37 uses a pilot bearing that is inside the flywheel vs inside the crankshaft for the 420g.

[bigjae46]

No they don't, you cannot remove a 420g and replace it with a ZF320 with no other mods. Basic rule is the transmission dictates the clutch (and flywheel), crossmember and shifter. Driveshafts have a couple variables because all of the transmissions are different in length/guibo size.

And that torque rating isn't a glass ceiling. IDK what it actually means but if that were the case all the turbo ZHPs would have blown up transmissions... think about how many SC/turbo S54/S52s are making well over 420nm and running 420g or ZF320s.

If you are concerned about it though then put in an S6-53 from an N54 335i.

Really just need to change the clutch disc with a 5 speed swap.

The ZF 6 speed has a different spline count than the 420g…I think. That’s the downside - clutch choices will be very limited. You can use…gulp…UUC.

I ran a ZF 6 speed with a twin screw kit in my 330 - 345whp and 300 ft/lbs. Never had a clutch or transmission issue. I’d be ok with an S54 and bolt on mods. Might be an issue with a lot of boost.

[George Hill]

Don't people plug and play the non M 5mt into M3s for track use? I've never heard of any input spine shaft issue for that (though admittedly never cared enough to look into it), and I'd have to imagine that's the same in the 5mt and 6mt.

... better not do any power mods of your S54. S6-37 is rated for 273 ft lbs of torque. Stock S54 comes with 269 ft lbs!

*Also the250g's DO have different spline counts based on year so that 100% is a thing on those transmissions... wouldn't surprise me if it is on others too.

[George Hill]

Don't people plug and play the non M 5mt into M3s for track use? I've never heard of any input spine shaft issue for that (though admittedly never cared enough to look into it), and I'd have to imagine that's the same in the 5mt and 6mt.

... better not do any power mods of your S54. S6-37 is rated for 273 ft lbs of torque. Stock S54 comes with 269 ft lbs!

No they don't, you cannot remove a 420g and replace it with a ZF320 with no other mods. Basic rule is the transmission dictates the clutch (and flywheel), crossmember and shifter. Driveshafts have a couple variables because all of the transmissions are different in length/guibo size.

And that torque rating isn't a glass ceiling. IDK what it actually means but if that were the case all the turbo ZHPs would have blown up transmissions... think about how many SC/turbo S54/S52s are making well over 420nm and running 420g or ZF320s.

If you are concerned about it though then put in an S6-53 from an N54 335i.

[Obioban]

bigjae46 Obioban

The S6-37 is such a good transmission ESPECIALLY compared to a 420g. I approve of swapping them in place of the 420g. To make the swap you would use everything from the E46 330 setup (clutch/flywheel and shifter). You'd probably need a custom drive shaft to work with the M3 diff though.

IIRC the difference in the M vs Non-M is the input shaft spline count, but I could be wrong.

Don't people plug and play the non M 5mt into M3s for track use? I've never heard of any input spine shaft issue for that (though admittedly never cared enough to look into it), and I'd have to imagine that's the same in the 5mt and 6mt.

... better not do any power mods of your S54. S6-37 is rated for 273 ft lbs of torque. Stock S54 comes with 269 ft lbs!

[George Hill]

bigjae46 Obioban

The S6-37 is such a good transmission ESPECIALLY compared to a 420g. I approve of swapping them in place of the 420g. To make the swap you would use everything from the E46 330 setup (clutch/flywheel and shifter). You'd probably need a custom drive shaft to work with the M3 diff though.

IIRC the difference in the M vs Non-M is the input shaft spline count, but I could be wrong.

[bigjae46]

Per BMW, 46kg for the 420g and 43.5kg for the 37BZ:
https://www.realoem.com/bmw/enUS/par...&q=23002229721
https://www.realoem.com/bmw/enUS/par...&q=23007837983

So, 5.5 lbs. If my trans fails I might go that route, but until that time... probably sticking with the 420g.

I do notice the PN for the Z4M box doesn't include anything other than the Z4... so maybe they used some sort of custom bell housing for the Z4M?

Yeah, not worth a swap but if replacing then a BMW reman would be the route I'd go.

[Obioban]

They used it on the Z4M, so you could probably just copy whatever they did there.

…. I wonder how the weight compares…

Per BMW, 46kg for the 420g and 43.5kg for the 37BZ:
https://www.realoem.com/bmw/enUS/par...&q=23002229721
https://www.realoem.com/bmw/enUS/par...&q=23007837983

So, 5.5 lbs. If my trans fails I might go that route, but until that time... probably sticking with the 420g.

I do notice the PN for the Z4M box doesn't include anything other than the Z4... so maybe they used some sort of custom bell housing for the Z4M?

[Obioban]

The ZF 6 speed in the non-Ms shift far better than the rubbery 420g. I think the input shaft is slightly shorter...so would it bolt onto an S54 with the non-M flywheel?

They used it on the Z4M, so you could probably just copy whatever they did there.

…. I wonder how the weight compares…

[bigjae46]

A ZHP? Now that's a good score! Those transmissions are $$$$.

The ZF 6 speed in the non-Ms shift far better than the rubbery 420g. I think the input shaft is slightly shorter...so would it bolt onto an S54 with the non-M flywheel?

[liam821]

usdmej.... Yes

A ZHP? Now that's a good score! Those transmissions are $$$$.

[George Hill]

usdmej.... Yes