gs6-45bz Rebuild Help

[khuang0925]

Hi guys, it has happened. My 2012 BMW 135i's 6 speed has lost the 1st to 2nd gear synchro. I am not sure about my next step, to swap another 45bz or do a 53bz conversion. I don't really want to go the first route since some day in the future same thing is going to happen again. I was doing some research and found that there are very few people that do rebuild here in the US. I was able to find a rebuild kit for it(first and second gear + the synchros) but I'm not sure if there's anyone here in California can even do the rebuild. Some recommendations for my next step will be greatly appreciated!

[moose09876]

Subscribed to this. I know I'll be in this spot someday.

[khuang0925]

Originally Posted by moose09876

Subscribed to this. I know I'll be in this spot someday.

It is inevitable , I know there’s a lot more people that rebuild gs645bz in the europe, just never heard about people who do that here. Hopefully could find someone who is capable of doing that, I heard it’s a pain to take apart this gearbox.

[drover135]

Originally Posted by khuang0925

I was able to find a rebuild kit for it(first and second gear + the synchros)

Do you mind sharing what kit you found? I’m in the same boat, mine grinds unless I baby it out of first, been wondering what to do about it for a year. I had no idea a kit existed.
I’m not in CA so I can’t help you with a shop, but I was just going to start calling all the BMW indies in the area and ask if they know of any tranny shops capable of opening these up

[khuang0925]

Originally Posted by drover135

Do you mind sharing what kit you found? I’m in the same boat, mine grinds unless I baby it out of first, been wondering what to do about it for a year. I had no idea a kit existed.
I’m not in CA so I can’t help you with a shop, but I was just going to start calling all the BMW indies in the area and ask if they know of any tranny shops capable of opening these up

I know some shops in China that rebuild gs645bz since the only model sold there with this gearbox was the 1M so when their gearbox go bad they have to rebuild instead of swapping, I could only found this picture of the brand for the 1st gear, but the kit they sell includes the 1st and 2nd gears plus the synchros.

[13A1AH]

I just want to clear up some stuff on the 45bz to 53bz trans swap I’ve seen after I’ve just done it to my 135i, I’ve seen a lot about how you can just press the input shaft from the n54 into the n55 flywheel, you can’t the shape of the rest for the flange on the backside of the input shaft doesn’t work correctly and the holes are different sizes. Also want to say that you can run the slave cylinder, and driveshaft from the n55 car. One more thing is that you do have to extend a little reverse wiring harness super easy just 2 wires. Hope I can clear some stuff up for some people save them a headache.
Also horsepower freaks and garageholics have good removal and install videos
If your having a hard time finding a 6 bolt n54 clutch look at X clutch kits, there’s also a spec single mass steel flywheel that I bought you will have some gear chatter if you run oem clutch like I did not too bad though.

[e80two]

Pick up an F8x 6MT, which is designed to handle more TQ.

https://www.1addicts.com/forums/show....php?t=2196170

[moose09876]

Originally Posted by e80two

Pick up an F8x 6MT, which is designed to handle more TQ.

https://www.1addicts.com/forums/show....php?t=2196170

Got any hookups for ones under $4k?

[moose09876]

Originally Posted by khuang0925

I know some shops in China that rebuild gs645bz since the only model sold there with this gearbox was the 1M so when their gearbox go bad they have to rebuild instead of swapping, I could only found this picture of the brand for the 1st gear, but the kit they sell includes the 1st and 2nd gears plus the synchros.

https://webshop.ganzeboom.net/gs6-45

So stupid. You can't see prices unless you're a transmission shop. And then they quote you more as an individual. Gatekeeping at its finest.

GS6-45.SEALKIT1 €65,00
GS6-45.GEAR-1ST €413
GS6-45.SYN.R-AM €138

[e80two]

Originally Posted by moose09876

Got any hookups for ones under $4k?

The unit I picked up came with the clutch and flywheel, and I was in for $2600. If you do some poking around, you can find one well under $4k. I'll reach out the the recycler that assisted me and see what he has in stock.

[khuang0925]

Originally Posted by e80two

Pick up an F8x 6MT, which is designed to handle more TQ.

https://www.1addicts.com/forums/show....php?t=2196170

WOW, the more I look into rebuilding the more I want to do a swap instead lol. Does the gs6-45bz on F8x not have synchro issue? I am looking into someone's post for a 53bz swap, not sure if I am capable of DIY this job.

[e80two]

Originally Posted by khuang0925

WOW, the more I look into rebuilding the more I want to do a swap instead lol. Does the gs6-45bz on F8x not have synchro issue? I am looking into someone's post for a 53bz swap, not sure if I am capable of DIY this job.

1) You'd be hard-pressed to find someone to do a rebuild.
2) It's even more difficult to find the parts.
3) The synchro issue will always be a thing with the stock transmission, even if you rebuild. The replacement parts haven't been strengthened any, so if it failed once....
4) The F80 is more robust (read the documentation via the links in my post)
5) The stock F80 clutch is rated to hold pretty much the same amount of tq as the aftermarket twin-disc I pulled out.
6) One of these transmissions is in supply and still made by BMW, the other is discontinued.

Kind of a no brainer, tbhwy. The synchos are the weak point of the N55E trans. It's well known and documented. To me, doing a rebuild of that transmission is throwing good money after bad.

[al_v]

Originally Posted by khuang0925

I know some shops in China that rebuild gs645bz since the only model sold there with this gearbox was the 1M so when their gearbox go bad they have to rebuild instead of swapping, I could only found this picture of the brand for the 1st gear, but the kit they sell includes the 1st and 2nd gears plus the synchros.

I've also have issue with 2nd gear. The image you sent is Masiero gearbox parts, they don't do 2nd gear, unfortunately.
So far I've found two companies that do rebuild, both in UK.
Bristol Transmissions and Gearbox Centre. Bristol don't do them anymore, gearbox centre, as far as i can see in their video, uses masiero kit and some second gear syncro, don't know where they got it. They said they can sell a kit, but price is unknown and you still need somebody, to rebuild it.

https://www.youtube.com/shorts/sZESpElztos