[Tomnavigator]

Has anyone or does anyone know someone that installed an 8HP transmission from a 535D in a 335D to replace their 6HP transmission? If so, I have a few questions.
1)what was/is the fuel mileage before and after in the car?
2) What is the 0-60 time?
3) What is the RPM at 70 mph?
4) Is the transmission an easy swap out?
5) What modifications were needed?
6) Was reprogramming the transmission module difficult? Where did you get the program for the transmission?
7) Would you do it again or stay with the 6HP if you had to do it over?

This swap seems like it would be a natural and beneficial modification for the 335d. First gear has a higher ratio which would improve take off acceleration and the eighth gear has a lower ratio which would lower the RPM which would reduce noise and increase fuel mileage. I would think it would improve the fuel mileage between 6% and 10%. The overall RPM should be about 14% lower.

[BB_cuda]

A guy on NABDOG is doing a M57 transplant into a 1 series but using a 8 HP transmission too. Don't think car is running yet but the guy is very competent so it should be soon.

[lnxguy]

I hope the OP isn't doing this to save money on fuel.

[Tomnavigator]

No. I am not doing a transmission swap and have no plans on doing one. It makes no sense to me to spend thousands of dollars to save a few hundred in fuel. However, I could see someone who needs to replace their transmission doing a swap out if they get the 8 speed cheap enough although it would be a lot of trouble because of programming issues.
I would still like to find out how it works out for the guy cuda referred to that is putting one in a 1 series. I think it is a natural swap for someone to do "just cause". Some people do things just for the challenge and to say they did it when no one else could.

[drg007]

love to have 8 speed on the 335D

[POBEP]

My uneducated guess that 6HP-to-8HP swap would be challenging but not impossible.

A more exiting, known-2-work option is 6HP to 6MT swap.
It is still involved effort, but result is far more desirable, especially E91+M57+6MT option.

[Persian Whisperjet]

Originally Posted by POBEP

My uneducated guess that 6HP-to-8HP swap would be challenging but not impossible.

A more exiting, known-2-work option is 6HP to 6MT swap.
It is still involved effort, but result is far more desirable, especially E91+M57+6MT option.

I believe Matt Whitbread was working on that using UK-sourced parts. The M57 power band is so wide though, you wonder if it would be much fun to have an MT.

[E85 Sport]

Bumping for more discussion about 6HP to 8HP swap.

In November 2022 this Bring A Trailer auction featured a car with our diesel engine M57 mated to ZF 8HP automatic:
No Reserve: M57 Diesel-Powered 2011 BMW 135i Coupe

Builder used aftermarket transmission control unit by TurboLamik.

Surely others have ventured down a similar path..

[POBEP]

Originally Posted by E85 Sport

Bumping for more discussion about 6HP to 8HP swap.

In November 2022 this Bring A Trailer auction featured a car with our diesel engine M57 mated to ZF 8HP automatic:
No Reserve: M57 Diesel-Powered 2011 BMW 135i Coupe

Builder used aftermarket transmission control unit by TurboLamik.

Surely others have ventured down a similar path..

I thought Redshift E91 wagon build was impressive, but this one is mind blowing ...

[POBEP]

Originally Posted by Persian Whisperjet

I believe Matt Whitbread was working on that using UK-sourced parts. The M57 power band is so wide though, you wonder if it would be much fun to have an MT.

All my BMW are AT. I just want an MT one, badly ... in the E91 body ... and with M57 ...

[lnxguy]

There are 8hp swap kits out on the market now. Source a tranny and buy the kit, I believe it's $2500 (sans tranny).