Are N54 and N55 DCT interchangeable?

Milan

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Does anyone know if all N series DCT trans are the same? I know the one out of the M3 has a a different bell housing.

I am considering a DCT swap and it would make my life a lot easier if I could source a trans out of a N55 car or Z4.

Also with XHP out now can I source 335is shifter or does it have to be m3?
 

martymil

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Much cheaper and easier to source a 335i n54 dct and far less headaches and transplant all your mods and sell your car.

I like the dct but I prefer auto much better for city driving and drag racing.

Clutches don't last forever in the dct and are expensive especially when racing or driving hard.

Don't get me wrong the DCT is brilliant and a hoot to drive but auto is heaps better and have you seen a shift with the
manufacturers back to auto, wonder why that is LOL.

The new autos are way stronger
 

aus335iguy

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E92 m3 is a different bellhousing yes. This is certain.
Most of the n54 and n55 DCTs are the same. The ones from the n55 and s55 M2 are different to N54 as they used different control methodology and use different ratios...
The f80 DCTs are different in that they are similar/same as the M2 ones( i think)

Please do your own research, I'm just some guy on the internet after all and its a lot of money if we get it wrong.
The way i remember it is...the gear ratios are a dead giveaway as is the SG or BG designation ;)

As for the manufacturers moving to Auto's .... Its just cheaper to get 90% of the result they need.
 
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aus335iguy

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A properly built auto is much better than dct in just about every way and with todays software control it will destroy them, just look at the 10 speed
behind the mustang, killer setup.
Which isn’t at all relevant because you can’t put those gearboxes behind an N54 easily.
the fastest autos still can’t do 80ms shifts which is why the Shelby gt500 which is the most powerful and most track focussed one has a DCT.
 

aus335iguy

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JPL Auto Parts has already put an 8 speed behind an n54 so itwon't be to long

Tom is a bloody genius with bmw electronics.

All one has to do is an adapter plate and he will do the rest.
Is that what your going to do ? Or are you going manual?
 

martymil

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I've got a brand new manual gearbox atm but I'm thinking to do the 8 speed in the 125i or buy a n55 135i and just do the n54 swap with the z4 35is INAMOS software. on my 1m ECU.

I have so many options open to me right now and will all cost me around the same so I'm leaning towards the n54 and 8 speed in the 125i.

No matter what its going to be a hoot and wickedly fast.
 

carabuser

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Software on the DCT is the same between the Z4, N54 and N55 cars. The calibration data is slightly different for each model to cater for the handbrake and mode selection differences but that can be flashed with WinKFP. Couldn't tell you of any physical differences though.


I don't get why you'd mentioned a slushbox at all. The 8AT is an improvement on the 6AT but it's still reserved for the comfy GT cars and lesser models. Even with the most aggressive tuning on the 8AT it feels soft and detached in comparison. Seems like a lot of effort without much reward to do an 8AT swap. If you're really into drag racing then isn't the powerglide swap more suited?
 

aus335iguy

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I’ve a hunch some of the later n55 cars were flex ray and might have a different TCU (physically) to allow for that?
 

martymil

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I have two transmission to choose from

the S55 dct or the 8at both a brilliant transmissions but If im going to drag race the 8at would be the choice.

In the end it comes down to money and with the 8at just getting better and better and with 1500hp upgrades available now I think we have a winner.
 

aus335iguy

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also the shifter from a 135is or 335is will work. XHP relies on the CAS module to decipher which box you have. If you dont have a DCT VIN it wont work. It will also flash DCT calibration on the box according to that VIN... IE M3 VIN = M3 flash and shifter.
 

Milan

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also the shifter from a 135is or 335is will work. XHP relies on the CAS module to decipher which box you have. If you dont have a DCT VIN it wont work. It will also flash DCT calibration on the box according to that VIN... IE M3 VIN = M3 flash and shifter.

Thank you. I both agree and disagree with Marty that the auto is better. Either way, I am somewhat set on doing the DCT swap as it has more cool factor, I will be removing my PD 6AT in order to do so.

I found a DCT out of 2012 135i today, so now I will start sourcing the other stuff.
 
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martymil

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Dude choose the transmission you want, all I'm saying is auto is better or drag racing and dct is better for track and street.

In the end its your car and how deep your pockets are and everybody has a different opinion.

As long as your happy with your choice is all that matters in the end.

I love my s65 1m and some people thing I'm crazy for doing this but there is always a reason for my madness and everything will make sense soon.
 

jakeg

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I used a n55 DCT in my DCT swap from a standard 135i and have zero issues. (Other than xhp being a headache lol) The only difference between e9x/e8x series DCTs is the bell housing and gearing. One bellhousing is for the s65, one is for the N series turbo motors.Gearing doesnt matter as you cant use the M3 DCT on n series engines anyway. The only DCT thatll fit is from any n54/5 cars.
 
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1DCTN54 Matt

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I used a n55 DCT in my DCT swap from a standard 135i and have zero issues. (Other than xhp being a headache lol) The only difference between e9x/e8x series DCTs is the bell housing and gearing. One bellhousing is for the s65, one is for the N series turbo motors.Gearing doesnt matter as you cant use the M3 DCT on n series engines anyway. The only DCT thatll fit is from any n54/5 cars.
dude story of my life, i had it going and reading out my CAS and it let me see the 7 speed map pack and wanted me to purchase a brand new license. when i went to put in my info the app crashed saying it wasn’t supportive 😭 buddy of mine has done the m3 GTS software and swap so i’m looking for answers this week.
 

martymil

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Has anybody ever done a DCT swap in a pre March 2007 build date. I have a 335i october 2006 build date.
Yes has been done but a major pain as it's an 8 bolt crank, you can get a 8 bolt dct flywheel but its like finding Unicorns.

You can buy them new but extremely expensive, the actuall conversion is way to expensive and it would be cheaper to sell and buy a new car, not kidding.
 

Tamaluko

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Yes has been done but a major pain as it's an 8 bolt crank, you can get a 8 bolt dct flywheel but its like finding Unicorns.

You can buy them new but extremely expensive, the actuall conversion is way to expensive and it would be cheaper to sell and buy a new car, not kidding.


Thanks for the reply Marty can you point me on who has done the pre March 2007 build date swap so I could ask them how it was done.

That hiccup with the 8 vs 6 bolt crank I know about. I wish I would've built my 6 bolt crank motor instead of my 8 bolt crank motor. 😪

I have literally everything for this swap already.
DCT, Drive Shaft, 2.56 Diff, JBE2, DSC Sensor, DSC module, GWS, park lockout and an 8 BOLT M-Factory SM Flywheel (I don't mind if it is noisy or causes vibrations it's it's racecar haha) , Just missing the Axles.

My concern is that the AT wiring harness from build date March 2007 and back have diffrent plugs in the E-Box. Compared to the post March 2007 cars. I have been trying to use ISTA to trace all the wiring down but it is such a pain. I miss NewTIS.

I think if I can get the EGS talking on the CAN line I can just take all the wires out of the existing ZF6HP plug and use ISTA to tell me what each one does so I can put them in the correct spot on the new DCT plug from MAXXEcu.


Thank you for the help I'm balls deep in the build. There is no going back now. It's either upgrade the AT or DCT swap.