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

[Obioban]

No comment on the 1-2 shift with the ZHP, but LT3 is not the same spec as the original factory fill...

[e46IX]

Alright making a return from my M3F hiatus to bump this thread. I've been in a Z4M coupe these last several years to get my S54 fix but I recently got another E46 M3 in my life that I'll be restoring.

So, I recently finished a SMG to Manual swap. Bought a used original manual 420G since I didn't want to mess around with machining work.

All new oem shifter bushings and fresh MTL-LT3 in there. Shifts like garbage.. sloppy, lots of play in gear, and takes quite a bit of persuasion to get it into gear when the trans is cold.

Now I'm no stranger to the 420G I know its always been a rough and noisy transmission, I feel like I got a high-mileage one with bad synchros or something since I just bought it used with no history on it. In retrospect I should have just paid a shop to convert my low-ish mileage SMG trans to manual but whatever that's already gone now.

I have the motor back out to refresh the whole thing on a stand, so now is a good time to consider swapping the trans. I can get a ZHP 6-speed easily through a buddy.

The Z4M 1-2 grind is a legit cause for concern, you can't go WOT and bang 1 to 2 in the Z4M. You have to baby that shift. The only good thing about the 420G is it takes a beating.

How many E46 M3's are out there running with the 330i/ZHP 6MT gearbox? Are the M3's with the ZHP trans also grinding that 1-2 shift? There's no solution in the Z4M world for this one, we just baby that shift.

I've had many ZHP's in the past, the ZF unit is nice in that car. It's smooth, quiet, and even when it's sloppy high mileage it still feels better than a sloppy 420G. The M3 driveshaft should bolt right up I don't think we even need to modify it.

[maupineda]

Z4M shift is pretty nice with the ASS kit, but it can groan into second if rushed at redline. All other shifts are crisp and direct.

[Obioban]

Are you sure that’s what you have? From what I’m seeing the 128 came with the S6-17. Which is going to be rated for less torque and is actually built by Getrag, not ZF

lol, and just like that I’m back in the game!

[terra]

I kind of lost interest once I realized I own a S6-37 already (in my 128i). I don’t think it shifts any better, even compared to the completely stock 420g in my e39 M5… much less compared to the auto solutions kit in my e46.

Are you sure that’s what you have? From what I’m seeing the 128 came with the S6-17. Which is going to be rated for less torque and is actually built by Getrag, not ZF

[kaiv]

I had a Z4M Coupe and 1-2 was notchy. And peoples on Zpost were also complaning about it over the years. Not sure it will be a night and day difference if someone do the swap.

A lot of complaints about that 1-2 upshift grinding at high rpms also on Z4M.

[kaiv]

What flywheel?

Couldn't say. Current owner acquired the car as-is and let's just say there is a lot of sorting out to do. If I find out I'll let you know.

[Obioban]

can the m5 lever be used in the m3 plug and play?

Don’t know at all.

I’m sure auto solutions would be happy to make a long shift kit.

[tlow98]

Longer throws.

can the m5 lever be used in the m3 plug and play?

[heinzboehmer]

The 3 piece synchronizer works very well when its New.
The moment they wear out little bit...is what everybody
is experiencing on G420 2nd gear and when cold its getting
worst till the oil gets thinner. 2nd gear is the most abused one
from all.

Yeah, that's why I want to swap the 420G out!

Never compare Cable sifter vs Rod direct shifter.

Agreed that it's pretty useless to compare them when talking about the mechanics of the system. However, I think it's totally fair to compare them when it comes to feel. At the end of the day, what I'm saying is that I really liked how the shifts in the 981 felt in my hand and I do not like how the shifts in my M3 feel.

Won't be able to completely replicate the feeling with a rod shifter unless I reengineer things so that I can use a cable shifter (which sounds like a complete waste of time). I would, however, like to get closer to that shift feel and the ZF boxes seem like the way to go (at least based on other BMWs I've driven with ZF boxes in them).

Edit: The cable shifter conversion actually sounds fun to design. I kinda want to do it now...

[Anri]

Notchy is fine with me, up to a certain point. What I hate about the 420G is how crunchy it feels. 1-2 shift requires way too much force and you have to crunch your way in. Feels like there's a few separate points where you encounter resistance in the throw.

+1 to the 981 comment. That gearbox feels amazing.

heinzboehmer,

The 3 piece synchronizer works very well when its New.
The moment they wear out little bit...is what everybody
is experiencing on G420 2nd gear and when cold its getting
worst till the oil gets thinner. 2nd gear is the most abused one
from all.

More often Engineers will overthink in order to make concept
to work better than the previous gen. Look at the S54 Vanos
and look at S65 Vanos...instead the S65 to be way more complicated
they when back worth way more simple unit over all in design
and package. I'd say almost like M50...(but not getting into details
on this one)

Never compare Cable sifter vs Rod direct shifter.

Regards,
Anri

[D-O]

Has anyone tried swapping in something really off the wall? Tremec maybe?

[D-O]

Longer throws.

Okay. So how would one replicate this in the M3? The list of things I don't like about my E46 M3 is extremely short, but shift feel is at the top of that list.

D-O

[Anri]

It shifts perfectly. Super communicative, super slick, it's buttery smooth. Have you driven an S2000 with fresh fluid?

Hi,

Yes I have driven s2k ones long time ago.

I knew exactly what you like. If I recall you had
E34M5 ? If you install E36 M3 97' shifter and
upgrade the bushings with firmer durometer, E46M3
tranny bushings and it will feel exactly what you
are after.


A lot of engineering has gone when the Factory
designed the shifting characteristics.

Gear box side:

- Synchro design 1 - 3 piece
- Synchro material brass, steel
- Oil Viscosity and additives
- Shifting rod arc depth
- Shifting rod arc transition
- Spring pressure lb/kg


From the Chassis side:

- Shifter arm single or double ear
- Shifter bushing rubber durometer (specific)
- Shifter knob inside rubber padding

Regards,
Anri

[Slideways]

BMW chose to market SMG2s and sell more cars; therefore, no revised manwell gearbox