[apv97]

Recently purchased a 2014 335i and love everything about it except for this one small (big) issue. Unfortunately didn't realize it during the test drive, but such is life.

Pretty sure the 2nd gear synchros are shot. Shifting from 1st to 2nd is very tricky. Below 3k rpm it's 100% smooth if I shift very slowly (~2s start to finish). Any faster and it will grind. Above 3k, it's just about impossible. Go to shift and it won't go into 2nd / will get a handful of beans.

Double clutching seems to help...I've had a few good shifts under moderate power via double clutching at medium speed (~1-1.5s shift). If I double clutch any faster it still seems to grind a bit going into 2nd.

So under normal everyday driving conditions, it isn't an issue at all...but I didn't buy a 335i 6MT to only be able to drive it at 80% or to never accelerate quickly off out of stoplights.

Surprisingly, I'm not seeing many threads on this on F30post. A few other Google searches yielded depressing results but would love to get a better understanding of my options. I'm relatively new to mechanical work, but my dad, who is nice enough to be willing to help me, has rebuilt four manual transmissions over the years and a 735iL auto transmission (multiple times). Is it possible to get the synchro parts via the transmission manufacturer and DIY this? Or is a refurb whole MT my only option? If so, how much does one of those cost? I read a dealership would charge up to 8k for the whole job...so that is NOT an option.

Thanks in advance.

[Billfitz]

A used transmission from a wreck would be the least expensive option. It's easier to replace a tranny than to rebuild one. https://www.newtis.info/tisv2/a/en/f...arbox/HCo8YhrZ

[apv97]

Thanks for the quick reply. What should I expect to pay for a wreck transmission and where would be a good place to find one? I guess you're rolling the dice that the wrecked one didn't have the same synchro issue...

Anyone done this DIY?

[thejeremyman9]

This has been discussed a few times. Unfortunately, to my knowledge, there are still no syncros nor rebuild kits avalable. A couple of forum members had their 6MT replaced due to a 2nd gear grind while still under warranty (the few mod-free folks who had a lease return beat on, for example) - that was a swap of a new transmission per BMW. As mentioned above it is basically considered a transmission replacement. Not sure on price honestly... Might have to try copart of a junk yard.

[F32Fleet]

BMW's are NOT BUILT for drag racing. Unfortunately there are too many knuckle heads who didn't get the memo.

The 1-2 shift is there just to get you going.
You're not supposed to rag out the car in first gear. No No No.

It's a BMW, not a 4 cylinder Honda Civic.

[apv97]

Originally Posted by F32Fleet

BMW's are NOT BUILT for drag racing. Unfortunately there are too many knuckle heads who didn't get the memo.

The 1-2 shift is there just to get you going.
You're not supposed to rag out the car in first gear. No No No.

It's a BMW, not a 4 cylinder Honda Civic.

Can't say I blame the previous owner. A car that does 0-60 in less than 5s and bills itself as the Ultimate Driving machine should be able to take upshifts near redline.

I don't plan on drag racing it, but it's getting old having cars go around me coming out of stoplights because I'm accelerating/shifting so slowly.

Continuing to look into the logistics of this transmission swap. I will have access to a 4 post lift in late October. Any tips on locating a solid used trans or walkthrough thread of someone doing this would be much appreciated.

[F32Fleet]

Originally Posted by apv97

Can't say I blame the previous owner. A car that does 0-60 in less than 5s and bills itself as the Ultimate Driving machine should be able to take upshifts near redline.

I don't plan on drag racing it, but it's getting old having cars go around me coming out of stoplights because I'm accelerating/shifting so slowly.

Continuing to look into the logistics of this transmission swap. I will have access to a 4 post lift in late October. Any tips on locating a solid used trans or walkthrough thread of someone doing this would be much appreciated.

Good luck

[cmart]

Originally Posted by apv97

Can't say I blame the previous owner. A car that does 0-60 in less than 5s and bills itself as the Ultimate Driving machine should be able to take upshifts near redline.

I don't plan on drag racing it, but it's getting old having cars go around me coming out of stoplights because I'm accelerating/shifting so slowly.

Continuing to look into the logistics of this transmission swap. I will have access to a 4 post lift in late October. Any tips on locating a solid used trans or walkthrough thread of someone doing this would be much appreciated.

Have you changed oil in your car? I too have a 335i 6MT with a rough 1-2 shift, I found if I pull it back into position without rushing it then it's fine.. also I just swapped my transfluid and it definitely improved the shift. I haven't had much luck finding replacements online but I know you can source one through a dealer.. honestly I might just take this car in and trade it to the dealer and get something else.. literally our stories are pretty similar, I didn't do a full rev 1-2 shift and when I tried later after getting more familiar it's grind city..

[apv97]

Bumping this up—swapped the 6MT fluid this week and no improvement. 4 post lift is finally here so ready to do the full trans swap but having trouble locating a donor. Need to do it in the next two weeks. Anyone know of any sites that might have a GS6-45BZ-THY8 transmission?

[apv97]

Follow up here: got an indy shop to do the full transmission swap + new clutch in November. Total price including parts and labor was $5100, which I felt was pretty reasonable given the transmission was bought directly through our local BMW dealer and I believe it came out to 4k for parts alone.

A very expensive fix for a poorly designed (weak) transmission, but it feels great to be able to drive the car normally (although I avoid high rpm 1-2 shifts...PTSD).