SMG to Manual Swap

[efrtysx]

Hello everyone hope y’all are having a good evening. I just had a shop convert my SMG to 6 speed manual. I was super excited until I picked it up. 1st and 2nd gear gets stuck as soon as I try to shift. I need to shift at an angle to make sure it goes straight into 2nd gear. I hate customers that are super picky and critical about everything, and I hate even bringing it up. But I can’t live with it. It’s super bad. I wouldn’t care if it was 5th or 6th gear, but it’s incredibly ridiculous to even drive the car. They’re telling me it’s an internal issue and not related to the actual bellhousing machining/installation. How could a 420g SMG transmission possibly have bad syncros, or internal wear? They are pretty much bulletproof. The hydraulic pump is what fails 90% of the time. I will be taking it back on Friday. Any advice on what it could be ?

[///Marecki]

maaaan this is my worst nightmare, I often consider doing my swap but I'm terrified someones gonna butcher it.

[ATB88]

Curious, which shop in LA is this?

[adr_M3]

I'm curious as well. I am looking to get the conversion done in the near future but unsure which shop in LA/SoCal is best suited to do the work competently, though I've read good things about Lang Racing and EAS in Anaheim.

[sapote]

1) 1st and 2nd gear gets stuck as soon as I try to shift. I need to shift at an angle to make sure it goes straight into 2nd gear. It’s super bad.
2) They’re telling me it’s an internal issue and not related to the actual bellhousing machining/installation. How could a 420g SMG transmission possibly have bad syncros, or internal wear? Any advice on what it could be ?

1) Too subjective from your description. Let's compare it with a "normal" or factory box: how much you need to pull to the left for 1/2 gears relative to 3/4 position? where is your 3/4 position vs "normal" box?

2) The required "deep angle" to get to 1/2 gears have nothing to do with the internal synchros condition.

[gheorghe]

H 1st and 2nd gear gets stuck as soon as I try to shift. I need to shift at an angle to make sure it goes straight into 2nd gear. I hate customers that are super picky and critical about everything, and I hate even bringing it up. But I can’t live with it. It’s super bad. I wouldn’t care if it was 5th or 6th gear, but it’s incredibly ridiculous to even drive the car. They’re telling me it’s an internal issue and not related to the actual bellhousing machining/installation.

I ran into the exact same issue during my SMG to 6-speed swap. The root cause was an off-center detent bore. In my case, it happened because I didn’t properly align the Bridgeport mill during bell housing machining.

It bothered me enough that I pulled the transmission back out and took it to a professional machine shop. They measured it with precision gauges and confirmed the bore was slightly misaligned. The fix was a custom detent pin machined to compensate for the offset.

By the time it was machined, hardened, and everything sorted out, it would’ve been cheaper to source a manual bellhousing from a wrecked M3. That said, it now shifts like a factory car.

Good luck but if you want it to shift properly you'd either have to take the route I did or find another bell housing.

[sapote]

I ran into the exact same issue during my SMG to 6-speed swap. The root cause was an off-center detent bore. In my case, it happened because I didn’t properly align the Bridgeport mill during bell housing machining.

It bothered me enough that I pulled the transmission back out and took it to a professional machine shop. They measured it with precision gauges and confirmed the bore was slightly misaligned. The fix was a custom detent pin machined to compensate for the offset.

By the time it was machined, hardened, and everything sorted out, it would’ve been cheaper to source a manual bellhousing from a wrecked M3. That said, it now shifts like a factory car.

Good luck but if you want it to shift properly you'd either have to take the route I did or find another bell housing.

This drawing has a problem: no reference to the centers of the new drilled holes. Do people just use the "holes" outside casting to find the bores centers? Casting is not precise though.

[gheorghe]

This drawing has a problem: no reference to the centers of the new drilled holes. Do people just use the "holes" outside casting to find the bores centers? Casting is not precise though.

Correct, the center line of the holes should align with the center point of each dowl that is pressed into the bellhousing. When I did mine, I pre drilled the cast holes to sight those dowels but i messed up the setting when I enlarged the holes to their final diameter. You don't have to be off by much to mess up the 1-2 shift

[efrtysx]

1) Too subjective from your description. Let's compare it with a "normal" or factory box: how much you need to pull to the left for 1/2 gears relative to 3/4 position? where is your 3/4 position vs "normal" box?

2) The required "deep angle" to get to 1/2 gears have nothing to do with the internal synchros condition.

You know what, from the driver position, if i try to go into 1st and 2nd (|) it doesnt go in at all. I need to move my elbow, in order to try and shift. (\) Every other gear functions properly. I’m thinking they made a mistake with one of the detents.

[efrtysx]

I ran into the exact same issue during my SMG to 6-speed swap. The root cause was an off-center detent bore. In my case, it happened because I didn’t properly align the Bridgeport mill during bell housing machining.

It bothered me enough that I pulled the transmission back out and took it to a professional machine shop. They measured it with precision gauges and confirmed the bore was slightly misaligned. The fix was a custom detent pin machined to compensate for the offset.

By the time it was machined, hardened, and everything sorted out, it would’ve been cheaper to source a manual bellhousing from a wrecked M3. That said, it now shifts like a factory car.

Good luck but if you want it to shift properly you'd either have to take the route I did or find another bell housing.

Wow that sounds like such a hassle. I’m sorry u had to go through that.

[sapote]

Correct, the center line of the holes should align with the center point of each dowl that is pressed into the bellhousing.

the dowels "A" and "B"? Why do you think the drilled hole center need to be lined up with the center of the dowel? The function of the dowel: "A" to stop the shifter passing the R gear and "B" to stop passing 5/6 gate. I don't see the logical connection of the detent sleeve holes and the dowels.

[1000hp]

If it's the original transmission, and it shifted properly when it was a SMG, it should shift properly now.

They F'd something up somewhere.