[Zbeck5]

Losing to an X5 has really done it for me. The 1-2 Shift Grind is becoming unbearable. I am MHD stage 2+, and overall the car runs great. I have been looking to add more power, but the transmission is first priority. After some fairly extensive searching and it seems there is 2 or 3 options.

Option 1: I can swap in a new factory replacement transmission from the dealer. Rough estimate $3500-$4500. New transmission, same design, and risk for failure in the future.

Option 2: Retrofit the GS6-53BZ from the N54 platform. This requires some modifications and fabrication, but it does not appear extensive. It seems the overall feel of the gearbox may not be as good, however it has proven to be more robust. The problem is finding a solid low miles unit for a decent price.

Option 3: Attempt to retrofit a GS6-45BZ-SHBT (From the F80 M3). I have not found evidence of this being done before. The transmission is longer overall, so it would require modification to the drive shafts, shifter, and who knows what else. I do engineer custom mechanical equipment for a living, and I have a very good BMW technician. I am confident we would figure it out eventually. But is it worth the time and effort?


Regardless of which path I choose. New brakes, suspension, and other upgrades will come with it. I have tracked it a few times now and it has shown its potential as it sits. The goal is to build this in to a serious track beast and also be able street drive as well. Not daily, but a cruise on a weekend. ANY feedback on experience with this situation is MUCH appreciated!

[dangerus_car]

If you are going to do 3, may as well swap engine to S55, as the transmission is what it is made for.

[thejeremyman9]

Someone did #2 and there is a thread about it in this section. Did you find that?

#1 - AFAIK no one rebuilds or updates the OEM 6MT, but about a year ago the same was true for 8AT and now Pure does it. Have you done an exhaustive search to confirm #1 upgrade is not an option?

[cookiemontis]

I would recommend swapping in a GS6-53BZ from an N54 donor car. I did this in my 2013 e92 335i and it shifts fantastic. If you buy a factory replacement you will regret it, 1-2 synchros are weak and it can't hold during high rpm shifts. I came across 4-5 used GS6-45BZ on eBay all stating slightly grinds in second.

If you are worried about buying a second hand GS6-53BZ, they are still available direct from bmw. Just get one for a 2013 335is. You will however need to confirm they will accept your old one as a valid core. I picked up mine used on eBay with 100k clocked on it for 1100.00 and have now put over 2000 miles on it with no issues.

I also was able to reuse my existing driveshaft. Given yours is an F series I am going to assume your going to need to modify the shift linkage/bracket since the GS6-53BZ never came factory in your model and it is about 1/2 inch longer than a GS6-45BZ.

Good luck.

[donkey]

FWIW I have a M2 which has the F80 transmission and the 1-2 shift is still rough. Not "grinding" as you mentioned but it feels the same as my F30 335i felt from 1-2.

I think that's just a BMW thing.

[Zbeck5]

Originally Posted by dangerus_car

If you are going to do 3, may as well swap engine to S55, as the transmission is what it is made for.

Yeah I would love to eventually, do not have the time for that extensive of a swap right now. I plan to try and build the N55 I have. Thinking forged rods/pistons, king rod bearings, maybe s55 oil pickup. Along with fueling upgrades and bigger turbo. I do not need insane power, but 500-550WHP would be great.

[Zbeck5]

Originally Posted by thejeremyman9

Someone did #2 and there is a thread about it in this section. Did you find that?

#1 - AFAIK no one rebuilds or updates the OEM 6MT, but about a year ago the same was true for 8AT and now Pure does it. Have you done an exhaustive search to confirm #1 upgrade is not an option?

I have spent probably 3-4 hours searching, and really have not seen anything. Sounds like something that is a replacement by BMW, and there is no service parts. Nobody has seriously taken the time develop their own package to upgrade. Hence why most people go for the 53bz it sounds like.

[Zbeck5]

Originally Posted by cookiemontis

I would recommend swapping in a GS6-53BZ from an N54 donor car. I did this in my 2013 e92 335i and it shifts fantastic. If you buy a factory replacement you will regret it, 1-2 synchros are weak and it can't hold during high rpm shifts. I came across 4-5 used GS6-45BZ on eBay all stating slightly grinds in second.

If you are worried about buying a second hand GS6-53BZ, they are still available direct from bmw. Just get one for a 2013 335is. You will however need to confirm they will accept your old one as a valid core. I picked up mine used on eBay with 100k clocked on it for 1100.00 and have now put over 2000 miles on it with no issues.

I also was able to reuse my existing driveshaft. Given yours is an F series I am going to assume your going to need to modify the shift linkage/bracket since the GS6-53BZ never came factory in your model and it is about 1/2 inch longer than a GS6-45BZ.

Good luck.

The shift linkage modification doesn’t seem very extensive. Just a little bit of low tolerance fabrication. I didn’t think about trying to pick up a new one from BMW. I will reach out to my local dealer to see what the price is for each transmission option. As much as I love the manual, it sounds like the 8AT might have had less headaches.

[Zbeck5]

Originally Posted by donkey

FWIW I have a M2 which has the F80 transmission and the 1-2 shift is still rough. Not "grinding" as you mentioned but it feels the same as my F30 335i felt from 1-2.

I think that's just a BMW thing.

How many miles, and have you ever done fluid change? I tried to do a fluid change to redline MTL once I started to notice, and it really didn’t make a difference.

Mine is way past rough, 30-40% of the time when I shift, even under 3k rpm, it grinds and doesn’t want to catch for like a second or so.

[cookiemontis]

Fluid change is not going to do anything, your 2nd gear synchro is toast and will only get worse. I am sure at this point downshifting grinds Everytime. I was in the same boat as you, finding out bmw does not provide internal service parts for any of their manual transmissions. Had I known this when I bought mine I would have gotten an automatic.

You can find second hand autos for 1/3 the cost of manuals as well which makes what your going through even more painful.

Your going to find the price for either manual version from BMW will be the same price. The one in the M3/4 is quite a bit more expensive and I am pretty sure has stronger internals. I was just not willing to be the guinea pig on trying to mate that in an e series when I knew the GS6-53BZ would drop in.

If you shop around there are other BMW dealers that have cheaper pricesl, you just need to see if shipping costs/core charges will negate picking up one locally.

[donkey]

Originally Posted by Zbeck5

How many miles, and have you ever done fluid change? I tried to do a fluid change to redline MTL once I started to notice, and it really didn’t make a difference.

Mine is way past rough, 30-40% of the time when I shift, even under 3k rpm, it grinds and doesn’t want to catch for like a second or so.

Only 16k on the M2 (just got it) and only ever got up to 6k on the 335i. No fluid changes.

I never had any grinding on that shift, but I can see how that could happen on either car.

I don't think I'd recommend upgrading to the F80 trans if you're targeting that specific issue. A lot of folks have mentioned the 1-2 is brutal on BMWs, so if it were me I'd hate to upgrade thinking it solved everything only to run into it again a few thousand miles later.

If it's that bad I'd probably go replacement trans and CDV delete.

[Zbeck5]

Does anyone know if there is a gear ratio difference from the gs6-45bz vs. gs6-53bz? I have read some posts claiming that the gear ration of the gs6-53bz from the n54 is "inferior" to the gear ratios of the gs-45bz. I have done some searching online looking for the gear ratios, and have not been able to find anything definite.

[MSPORT62]

Has anyone heard of a synchro replacement on these cars because others do just not one for the n55, I have the same problem

[burl25]

Howdy

You cant replace the synchros - non-serviceable part

These are basically the only threads I could ever find on the topic
Yes you can swap an N54 gen 6MT to an N55 in an f30. Two snags: Shift linkage bracket, and the neutral position sensor.

https://www.1addicts.com/forums/show....php?t=1632598
https://f30.bimmerpost.com/forums/sh....php?t=1855290
https://f30.bimmerpost.com/forums/sh....php?t=1855290

[-Eidos]

Originally Posted by Zbeck5

Option 3: Attempt to retrofit a GS6-45BZ-SHBT (From the F80 M3). I have not found evidence of this being done before. The transmission is longer overall, so it would require modification to the drive shafts, shifter, and who knows what else. I do engineer custom mechanical equipment for a living, and I have a very good BMW technician. I am confident we would figure it out eventually. But is it worth the time and effort?

If you're an engineer by trade, you have the potential to do the 6spd community a huge service by designing a bell housing/adapter plate to fit a T56 trans. May have to mess with wiring and what not for gear positions, but I'm sure it's possible.

Something like this was made for E36 M3s (S52): https://www.holley.com/products/driv.../parts/RM-4089