Replacing Tired Manual Trans w/ SMG trans

[beefaroni]

Those who recognize my michelin man avatar have had to endure a few of my complaints about the notchiness and shift quality of my manual transmission. I would assume the trans oil was still original at 150k miles.

I have fresh Pentosin MTF-2, upgraded shifter, new engine mounts. The slow crunchy shifts into every gear are the most disappointing part of the car. After maybe 20 miles of driving on a warm day the trans has enough heat to where the shift quality doesn’t catch my attention.

I have been looking for a lower mile spare trans to swap in this winter.

Does it make sense to seek out a lower mile SMG transmission (then add the detents, swap the bellhousing etc.) since you could argue that it has been properly shifted and has less wear on the internals?

someone please tell me my logic sucks and to stop overthinking it, also please sell me your transmission.

that would be gr8

[Icecream]

Those who recognize my michelin man avatar have had to endure a few of my complaints about the notchiness and shift quality of my manual transmission. I would assume the trans oil was still original at 150k miles.

I have fresh Pentosin MTF-2, upgraded shifter, new engine mounts. The slow crunchy shifts into every gear are the most disappointing part of the car. After maybe 20 miles of driving on a warm day the trans has enough heat to where the shift quality doesn’t catch my attention.

I have been looking for a lower mile spare trans to swap in this winter.

Does it make sense to seek out a lower mile SMG transmission (then add the detents, swap the bellhousing etc.) since you could argue that it has been properly shifted and has less wear on the internals?

someone please tell me my logic sucks and to stop overthinking it, also please sell me your transmission.

that would be gr8

I would for sure go that route unless I found a low mile manual. Should be easy to find an SMG transmission too.

[beefaroni]

It makes me feel slightly better that European Car magazine notes the notchy feel even when new

[r4dr]

Ideal case would probably be an SMG car being parted out.

[mrgizmo04]

If you have a self centering shifter (ala CAE), you dont need the bellhousing machined.

I actually swapped an SMG tranny with 50k miles into my car (swapped bellhousings also). I can tell you it feels basically the same as my old 6mt box. One other thing that I noticed on the smg tranny is that 4th gear synchro is a bit off and grinds a bit sometimes. I have also heard cases with 4th gears blowing up on smg boxes in smg cars. I am not sure why. I dont know how widespread this is, but I was surprised to have it in a 50k mile box.

Sent from my SM-G950U using Tapatalk

[eacmen]

I would try to use the bellhousing from your 6MT on the SMG trans you acquire. While many have had success with the self-centering shifters without detents the *one* car I drove with that type of conversion I was not impressed.

Others have reported great success with CAE-style shifters and I don't want to discredit them but my personal experience was less than stellar.

I concur with the article posted, on track the 6MT shifts *way* smoother than it does on the street. I never had a misshift even on a 96k fairly tired tranny with OEM shifter linkage.

[ethan]

On m3f the argument was often made that, IIRC, the input shaft bearing halves mate together with wear and therefore bellhousings shouldn't be swapped across different transmissions. They're probably right, but I just switch them around willy nilly and haven't blown anything up yet.

[eacmen]

On m3f the argument was often made that, IIRC, the input shaft bearing halves mate together with wear and therefore bellhousings shouldn't be swapped across different transmissions. They're probably right, but I just switch them around willy nilly and haven't blown anything up yet.

Wasn't aware of that good to know. I have never done the job myself, just driven cars that have had the swap done.

[ethan]

Wasn't aware of that good to know. I have never done the job myself, just driven cars that have had the swap done.

Risk worth taking as far as I'm concerned, but figured I'd put it out there.

[Steve]

Shift quality isn't that great in either of mine.

But yes, a used SMG transmission would be a safer bet than an unknown manual replacement. The other issue you'd run into would be the gear position sensor not being a direct bolt on.

[mrgizmo04]

Shift quality isn't that great in either of mine.

But yes, a used SMG transmission would be a safer bet than an unknown manual replacement. The other issue you'd run into would be the gear position sensor not being a direct bolt on.

Yeah agree, getting an smg that gets slammed by the actuator vs a "racing driver" banging the 6mt box is a better choice.

GPS is a quick job with the right bottoming tap and some grease.

Sent from my SM-G950U using Tapatalk

[beefaroni]

What is the purpose of the gear position sensor in the MT? is there torque limiting in 1st gear?

[mrgizmo04]

What is the purpose of the gear position sensor in the MT? is there torque limiting in 1st gear?

One is for cruise control, the other I don't remember.

Sent from my SM-G950U using Tapatalk

[ATB88]

Nah, I'm pretty sure it's just so that it knows whether or not you're in gear for cruise control, and possibly also used for knowing that you're in reverse (for PDC and reverse mirror tilt). But you can get those functions to work perfectly via some easy coding without needing to have an actual gear position sensor in place. While it makes the conversion more "factory" it's honestly something that's just not worth the trouble of doing unless you are going to go through every other little detail to make it "factory perfect", at which point you wouldn't be using an SMG transmission anyway. You don't need it for any functionality, so it's just for looks/"originality". I tapped threads into my SMG gearbox when I did my swap and it was just a big unnecessary PITA. Also, I think my trans is now leaking from the GPS 🤦♂️