[Ryanfknt]

As we all know or as you will quickly find out, the transmission that is paired up with the n55 6mt is fragile. Or complete junk. Call it as you want. It fkn sucks. The synchros are made of glass and many people have needed to replace them (very expensive)

I drive a 2014 f30 335i xdrive. The second gear synchro is bad. After lots of research, I decided the stronger alternative is from the older cars equipped with the n54. I bought a complete trans, shift bracket, with front and rear driveshaft from a 2010 335i xdrive.

I’m just going to list some things for other people to use that have similar interest.

The n55 is equipped with the gs6-45bz
The n54 is equipped with the gs6-53bz


The two best posts that I found that convinced me to follow through with this.
https://www.1addicts.com/forums/show....php?t=1386237
https://www.1addicts.com/forums/show....php?t=1632598

The posts above say to swap in to the n54 shift bracket, and you need the n54 front and rear driveshaft to make up for the different length of the trans.
I now have my gs6-45bz removed and sitting next to the gs6-53bz that I bought:
measurements from the bell housing show both front and rear driveshaft are exactly the same distance from the bell housing on both transmisssions. So with the two transmissions I have, I don’t need to swap to different driveshafts.
Measured to the front edge of the bell housing, The center of the shifter with the n54 shift bracket actually sits 3/4” closer to the front of the vehicle. I haven’t finished install so I don’t know how much of a problem this will cause.

Things to know:
Have to extend one wiring harness (I believe it is a 2 prong harness)
gs6-45bz pilot bearing in the flywheel
gs6-53bz pilot bearing on the trans (Input shaft on the flywheel)
My solution: Spec 2+ Clutch with steel SMFW for 2010 335i (comes with input shaft on the flywheel)

The only thing that makes the xdrive more difficult is the distance to reach “the bitch clip” on top of the tranny. My clips were seized on there so I just cut the shift bracket off because I am using the bracket from the n54. But HOLY SH$T this tranny is EASY work. The top two bolts on the bell housing I could get right through the top without any assistance, just lots of extensions. I don’t know why anybody would need to fish through under the hood while having assistance underneath. It is a clear path to EVERY SINGLE bell housing bolts once you drop down the tranny mount. Like seriously this was way easier than I expected. It’s actually fun how easy this trans was to remove.

I’m still in the middle of the swap, I don’t really have any questions, and I and a total noob. I just wanted to post all the information I could on it because it has been so damn hard to find anything at all diy on the f30 n55.

One thing I can’t find is how to do the rear main seal. That’s where I am right now on google.. and I am interested in seeing how the shift bracket will work out with it being 3/4” forward. I will be sure to keep this post updated!!

[-Eidos]

Good stuff! Love to see continual development on the N55 platform.

[Ryanfknt]

Neither of the shift brackets line up.
I am now looking for some sort of adjustable shift linkage.

Any suggestions let me know!! The shift bracket is aluminum and the linkage is steel. I am a fabricator so I may just add an inch onto both.. or some sort of adjustable linkage to purchase would be pretty neat

[XutvJet]

This swap doesn't make much sense at all. The 45bz is stronger than the 53bz. Did you miss the point in the link where they said the more powerful 1M ran the 45bz vs the 53bz? The M2/3/4 run the 45bz too.

The 45bz has upgraded synchros as well. Yes, they can and do munch the 1-2 syncro, largely because of added torque from aftermarket mods and hard shifting. Also, the XDrive puts a ton of stress on the synchros because of the additional traction.

[Ryanfknt]

Originally Posted by XutvJet

This swap doesn't make much sense at all. The 45bz is stronger than the 53bz. Did you miss the point in the link where they said the more powerful 1M ran the 45bz vs the 53bz? The M2/3/4 run the 45bz too.

The 45bz has upgraded synchros as well. Yes, they can and do munch the 1-2 syncro, largely because of added torque from aftermarket mods and hard shifting. Also, the XDrive puts a ton of stress on the synchros because of the additional traction.

There is a few different versions of the 45bz.
The 1 series M (N54) M2,M3,M4 all ran the 45bz. The 45bz that bolts to these M cars have upgraded synchros and larger bell housing/different bolt pattern than the 45bz that is is in the n55 335i. The 45bz in the n55 335 have very weak synchros.

From my understanding, In 2010, BMW decided the 53bz in the 335’s were overbuilt. From there, BMW built them to feel a little “smoother and luxurious” at the cost of strength. This is the 45bz that they put in the n55 335’s. Much different than the 45bz’s that are used on the M1, M2, M3, M4.

[Orion4]

My 13 335I Sportline ZF has been bulletproof so far (166,400). My kind of "junk"!

[Ryanfknt]

On the back of the n54 trans that I installed, right below the rear driveshaft, there is a transfer case resistor. The oem trans + tcase that I removed does not have a transfer case resistor. What do I plug into this resistor?? the wiring harness doesn’t have anything to plug into it because my old trans didn’t have this resistor.

I test drove it without anything plugged into it and it had a ABS warning etc, ( no sport mode) no CEL, but plugged into a snap on computer and we got
D356E4 - Message fault (status of distribution of the longitudinal torque on the front axle rear axle, ID:
ST_REPAT_XTRQ_FTAX_BAX) – Timeout

I believe this has to do with the transfer case resistor being unplugged. What do I plug into this resistor??


#14 is the resistor that the new tcase has on it.. the old tranny does not have this!!

[Ryanfknt]

Another issue / question I ran into is on top of the oem trans (2014 335i n55 trans (gs6-45bz) there was a sensor mounted to the top. It’s called a zero sensor / neutral position sensor. It is #6 in the picture below.

The trans that I installed (2010 335i trans (53bz) does not have this zero sensor and has no place to mount it. I just unbolted it from the old trans and zip tied it somewhere random on the new trans. It has no holes on the top to bolt it into like my old trans did.

[n55david]

Originally Posted by Ryanfknt

On the back of the n54 trans that I installed, right below the rear driveshaft, there is a transfer case resistor. The oem trans + tcase that I removed does not have a transfer case resistor. What do I plug into this resistor?? the wiring harness doesn’t have anything to plug into it because my old trans didn’t have this resistor.

I test drove it without anything plugged into it and it had a ABS warning etc, ( no sport mode) no CEL, but plugged into a snap on computer and we got
D356E4 - Message fault (status of distribution of the longitudinal torque on the front axle rear axle, ID:
ST_REPAT_XTRQ_FTAX_BAX) – Timeout

I believe this has to do with the transfer case resistor being unplugged. What do I plug into this resistor??


#14 is the resistor that the new tcase has on it.. the old tranny does not have this!!

no idea.. never tried to do that swap

[thejeremyman9]

Originally Posted by Ryanfknt

Another issue / question I ran into is on top of the oem trans (2014 335i n55 trans (gs6-45bz) there was a sensor mounted to the top. It’s called a zero sensor / neutral position sensor. It is #6 in the picture below.

The trans that I installed (2010 335i trans (53bz) does not have this zero sensor and has no place to mount it. I just unbolted it from the old trans and zip tied it somewhere random on the new trans. It has no holes on the top to bolt it into like my old trans did.

So if this isnt plugged in, does the car think it is in neutral all the time, or in gear all the time?

[Ryanfknt]

Hey jeremy I’m not entirely sure what the zero sensor does. I think it has something to do with the auto start/stop feature.. tbh I have no idea I can’t find much info on it.. BUT this is the sensor that sits on top of the trans, and it is plugged into the harness. I simply unbolted it off the top of the old trans and left it chilling up there. not bolted on to anything.. it’s just chilling.. idk what it does ..

The car drives amazing, new clutch is great, all gears engage and disengage.. it’s not in limp mode , just unable to use sport mode.. feels sooo amazing rowing through the gears on this new trans 😁😁😁 feels like a huge success, with just these small quirks left to figure out.

I’m worried about the only sensor that doesn’t have anything plugged into it.. the tcase resistor. I believe this is the reason for the code I’m throwing, causing abs issues etc , not allowing my car into sport mode

[thejeremyman9]

Originally Posted by Ryanfknt

Hey jeremy I’m not entirely sure what the zero sensor does. I think it has something to do with the auto start/stop feature.. tbh I have no idea I can’t find much info on it.. BUT this is the sensor that sits on top of the trans, and it is plugged into the harness. I simply unbolted it off the top of the old trans and left it chilling up there. not bolted on to anything.. it’s just chilling.. idk what it does ..

The car drives amazing, new clutch is great, all gears engage and disengage.. it’s not in limp mode , just unable to use sport mode.. feels sooo amazing rowing through the gears on this new trans ������ feels like a huge success, with just these small quirks left to figure out.

I’m worried about the only sensor that doesn’t have anything plugged into it.. the tcase resistor. I believe this is the reason for the code I’m throwing, causing abs issues etc , not allowing my car into sport mode

I am a little confused by that sensor though - didnt you say the car originally had no sensor there, so there was no harness/connection for it. But, the N54 trans does have that resistor/sensor?

If the car originally had no harness or sensor for it, how does it have any idea something is different or is now there that wasnt before? If the car didnt originally have it and there is no harness for it i don't see how it could throw a code because of that. To the car, it doesnt exist.

[n55david]

Originally Posted by thejeremyman9

I am a little confused by that sensor though - didnt you say the car originally had no sensor there, so there was no harness/connection for it. But, the N54 trans does have that resistor/sensor?

If the car originally had no harness or sensor for it, how does it have any idea something is different or is now there that wasnt before? If the car didnt originally have it and there is no harness for it i don't see how it could throw a code because of that. To the car, it doesnt exist.

you're correct.

ita just a guess but I'm assuming that sensor or whatever is built into another sensor or something else on the n55 version. so because of that he won't ever be able to get that part fixed.

I still think this whole swap was a huge waste of time but whatever, not my money.

[thejeremyman9]

Originally Posted by Phantom10R

you're correct.

ita just a guess but I'm assuming that sensor or whatever is built into another sensor or something else on the n55 version. so because of that he won't ever be able to get that part fixed.

I still think this whole swap was a huge waste of time but whatever, not my money.

I think its the OTHER sensor that is the problem - the neutral one or whatever. That's the one the car knows is there, but it does not have a place to be on the N54 trans. You would need to understand what is does and how it works to figure out a workaround... like grounding it or something, depending on what it expects.

[Ryanfknt]

Originally Posted by Phantom10R

you're correct.

ita just a guess but I'm assuming that sensor or whatever is built into another sensor or something else on the n55 version. so because of that he won't ever be able to get that part fixed.

I still think this whole swap was a huge waste of time but whatever, not my money.

Yes I agree with you that seems to be an accurate guess. Thank you. That’s where I’m at. I’m going to have to find a way to make it work.

I find it unusual you are not the first person to comment about this swap being pointless. Please explain what you would do if your transmission needed replacement because the second gear synchro is shot and your research pulls up countless proof that this trans will likely pull up the same issue again if buying another used one? Might even come back again if spending $4500 on a refurbished trans?

The n54 trans is stronger, and only cost me $800. From my research I didn’t expect to run into the issue of having a transfer case resistor on this new trans that my n55 wiring harness didn’t have a plug in for. There is limited information on this stuff and I’m trying to improve the forums with keeping our people posted with any information available on such.

The gs6-53-bz (n54 trans) rating starts at 600nm input torque and has a wet sump and it can be notchy and feel like a truck and gears can be easily missed so BMW went with the gs6-45-bz (n55) rating starts at 450nm input torque and has a dry sump and is silky smooth operation aimed at luxury at a sacrifice of strengh.

I linked 2 links in my first post of lots of people having this same issue and following through with this exact swap for these reasons. I believe the difference between the successful swaps I’ve seen, and mine; is that mine is xdrive.

Heres another post with people talking about this subject. Page 2-3
https://www.***********.com/showthre...-synchro-on-it

Waste of time? Maybe if I can’t make it work, but this swap was a viable upgrade for many other folk running rwd, but maybe xdrive is making this an impossible venture? I think not. I’ll figure it out.

Any help would be great! I need to figure out what to plug into this tcase resistor. Maybe I can plug my old tcase into my new n54 transmission instead?

[Ryanfknt]

Originally Posted by thejeremyman9

I think its the OTHER sensor that is the problem - the neutral one or whatever. That's the one the car knows is there, but it does not have a place to be on the N54 trans. You would need to understand what is does and how it works to figure out a workaround... like grounding it or something, depending on what it expects.

Yes the neutral/zero sensor. I need to figure out what exactly that sensor is looking for.. it just bolted onto the top of the trans.. does it thrive on just being mounted on the trans? Can I just drill it into the top of the new trans and it’ll be happy? These are questions for a very skilled bmw mechanic 😔 I’m searching local for the right people and I have the budget to pay my way through this venture. I hope

[terryd5150]

Originally Posted by Ryanfknt

As we all know or as you will quickly find out, the transmission that is paired up with the n55 6mt is fragile. I will be sure to keep this post updated!!

Some questions:

1. Could you disassemble the stock transmission case to see what sensor is tapping into to read? It might give you clues so you could rig an external dummy sensor onto the current set-up.

2. Would a 6MT from a 2015-2019 M4 fit and restore functionality - would it have that sensor port in it? Is the bellhousing pattern the same (I'm thinking an F32 N55)?

Regardless, awesome job on this project and thanks for sharing!

[terryd5150]

Originally Posted by Ryanfknt

Yes the neutral/zero sensor. I need to figure out what exactly that sensor is looking for.. it just bolted onto the top of the trans.. does it thrive on just being mounted on the trans? Can I just drill it into the top of the new trans and it’ll be happy? These are questions for a very skilled bmw mechanic 😔 I’m searching local for the right people and I have the budget to pay my way through this venture. I hope

Ryanfknt that neutral zero sensor may have a coding solution.

Apparently it has a range it expects to be in and you're falling outside that range - it needs to be recalibrated to the new range in INPA.

https://www.e90post.com/forums/showthread.php?t=1131209

[XutvJet]

Again, this mod makes no sense. The reason the bell housing is different on the M cars is because they have a different flywheel and clutch. BMW uses the 45BZ in the M cars because it's stout.

The reason your original 6MT is toast is because you've got AWD. It's basically like running drag tires all the time. If you launch hard or shift hard, especially with mods, you're putting a hell of a lot of stress on transmission because the tires won't break loose and take some load off. BMW offering a 6mt in the turbo AWD cars was a huge mistake from a long term reliability standpoint. I don't know of a single high powered AWD manual transmission car in existence that doesn't have an issue with breaking some component in the transmission or transfer case. In the 45bz, that weak link is the 1-2 syncro..

[Ryanfknt]

The problem was that the E90 tcase has the tcase resistor but my f30 trans harness did not have that. That was putting me in limp mode etc..

I took the tcase off my old trans and it bolted right onto the E90 trans. Same length, no problems. Check engine lights are gone, no more limp mode. Everything is good!!

I do still have “automatic start/stop malfunction” because of the zero neutral sensor on top of the trans.
This doesn’t effect driveability
Maybe I can find a way to code that out??

overall; MSSION SUCCESS 🍻

[Ryanfknt]

Originally Posted by XutvJet

Again, this mod makes no sense. The reason the bell housing is different on the M cars is because they have a different flywheel and clutch. BMW uses the 45BZ in the M cars because it's stout.

The reason your original 6MT is toast is because you've got AWD. It's basically like running drag tires all the time. If you launch hard or shift hard, especially with mods, you're putting a hell of a lot of stress on transmission because the tires won't break loose and take some load off. BMW offering a 6mt in the turbo AWD cars was a huge mistake from a long term reliability standpoint. I don't know of a single high powered AWD manual transmission car in existence that doesn't have an issue with breaking some component in the transmission or transfer case. In the 45bz, that weak link is the 1-2 syncro..

Thanks for your input again, I already responded to this previously if you look up in the post.

The 335i trans is different from the 45bz used in the M cars. The 45bz used in the M cars have upgrades synchros. They gave the trans the same name for some reason even though the 45bz In the M cars have upgraded internals and a different bolt pattern.

From my previous response to this:
“The n54 trans is stronger than the trans used in the f30 335i and only cost me $800.

The gs6-53-bz (n54 trans) rating starts at 600nm input torque and has a wet sump and it can be notchy and feel like a truck and gears can be easily missed so BMW went with the gs6-45-bz (n55) rating starts at 450nm input torque and has a dry sump and is silky smooth operation aimed at luxury at a sacrifice of strengh.”

[thejeremyman9]

Originally Posted by Ryanfknt

The problem was that the E90 tcase has the tcase resistor but my f30 trans harness did not have that. That was putting me in limp mode etc..

I took the tcase off my old trans and it bolted right onto the E90 trans. Same length, no problems. Check engine lights are gone, no more limp mode. Everything is good!!

I do still have “automatic start/stop malfunction” because of the zero neutral sensor on top of the trans.
This doesn’t effect driveability
Maybe I can find a way to code that out??

overall; MSSION SUCCESS 🍻

Congrats man, regardless of what anyone thinks you did it