[cmbe92guy]

Hello all,

Creating this thread to document swapping an 8hp45x into an 2011 335i xdrive. 8hp swaps are gaining popularity given the rise of AM transmission controllers (e.g. CANTCU, TurboLamik, HTG). This thread may be of interest to those looking for a plug and play, straightforward swap for their n55-powered e9x awd car.

Let’s begin with some barebones logistics:

1.) I used a 53k mile 8hp45x transmission from an f25 x3. I purchased the transmission through the straight six auto parts eBay store.
2.) I chose to use the CANTCU transmission controller. The CANTCU is essentially a CAN translator, allowing the e9x DME outputs/inputs to mesh with the stock, f-series 8hp TCU. The CANTCU provides nearly OEM integration and can be optioned with a PNP wiring harness. Kenneth from CANTCU is also extremely responsive and updates a ‘wiki page’ that is massively helpful.
3.) The car will need to be at least two feet off the ground to clear the old/new transmissions. I used some six-ton Habor Freight jackstands to reach that height. A swap of this type can be done on jackstands.

Let me know what would be helpful to see next. We can talk comphrensive parts lists, a how-to guide, costs, etc. I am nearing completion of the swap and am excited to see this sort of thing take over the BMW aftermarket in the near future.

[smass]

This is going to be my next project on my 2010 335i. I have the 8HP in a few other cars and it is awesome.

[cmbe92guy]

Originally Posted by smass

This is going to be my next project on my 2010 335i. I have the 8HP in a few other cars and it is awesome.

Agreed. The slushbox 6hp is the only thing wrong with the e9x non-M cars imo.

[e90yyc]

Awesome project! The 8HP is such a sweet unit… Looking forward to hearing more when it’s done!

[cmbe92guy]

Project has been on hold while I figure out how to cool the 8hp. Have been considering a full AN set up, a mix between factory hard lines and AN lines, and a mix between factory 8hp hard lines and e9x 6hp hard lines.

I decided to remove the factory 6hp cooler lines to start. Total PITA. Had to remove belt and power steering pump to fish the lines out. Ended up cutting them in several places. Job may have been easier if I removed the subframe. I was not keen on doing that again lol.

On an AWD e9x car, there is not much room to run cooler lines up to the front bumper. The steering shaft, drivers side motor mount, PS reservoir lines, charge pipe, and heater core lines all limit plumbing options.

[cmbe92guy]

So, I cut the 8hp line in attempt to mirror the factory e9x line. It turns out that the first foot or so of the 8hp line is nearly identical to the e series hardware. Both sets of lines clear the front drive shaft well and use the same mounting points on the block. Small victory.

I still have not figured out how I’ll manuver the 8hp line toward the driver’s side wheel well for the cooler. See attached pic to get an idea of the obstacles in place 😒 also haven’t considered where/how to mount a thermostat. There is still a long way to go…

[cmbe92guy]

Upon further thought, I’ve decided that an OEM hardline/AN line set up isn’t a great idea. The OEM hardline is made of a funky material that is not well suited for a barb fitting or a AN-capable 37 degree flare. Waisted 80 bucks on the 8hp lines and a couple hours with the dremel. Dang.

I’ve switched directions to an entirely AN set up. It’s coming along nicely. The improved racing T stat will mount neatly on some factory studs near the driver’s side strut tower. I hope to snake the braided lines around the strut tower via 45 degree fittings off of the T stat.

I found an old eBay oil cooler sitting around in the garage that I’ll use for the cooler itself. The cooler original used 10- AN bungs. I installed some 10 AN to 8 AN reducers to match my set up.

Next step is to mount the cooler in the driver’s wheel well.

[cmbe92guy]

Trans to T stat lines installed.

[cmbe92guy]

Oil cooler set up is temporarily rigged for a first start. Will use a 304 stainless bracket to mount the cooler to the crash bar studs. Now to attach the drive shaft/ exhaust. Hopefully will be able to connect the battery today!

[ky0u]

Originally Posted by cmbe92guy

2.) I chose to use the CANTCU transmission controller. The CANTCU is essentially a CAN translator, allowing the e9x DME outputs/inputs to mesh with the stock, f-series 8hp TCU. The CANTCU provides nearly OEM integration and can be optioned with a PNP wiring harness. Kenneth from CANTCU is also extremely responsive and updates a ‘wiki page’ that is massively helpful.

Would you happen to know if this set up affects the ability for Transmission flash tunes like xhp?

[cmbe92guy]

Originally Posted by ky0u

Would you happen to know if this set up affects the ability for Transmission flash tunes like xhp?

The CANTCU allows for aftermarket TCU flashes. I plan on using xhp once my swap is up and running.

[cmbe92guy]

Connected the battery and booted up the CANTCU configurator. CAN 1, 2, and 3 are registering load— thankfully I’ve wired the CANTCU correctly. In the midst of a ‘while-you’re
-in-there’ rust repair. Engine bay is buttoned up. Hopefully I’ll be able to start the car this week.

[cmbe92guy]

Kenneth is a blessing! Remoting in at almost 12am his time to defeat the TCU immobilizer/do some additional coding.

[cmbe92guy]

The swap is mechanically done. No leaks. Completed the transmission fill procedure after school today. Trans shifts smoothly through PRND/M1/M2 on stands. Next step is to attach the front D shaft and button up the underside. Also need to permanently mount the oil cooler using the factory crash bar studs. I’m going to do a few more runs up to temp before I set the car down. On the road soon!

[TyroneShoelaces]

Originally Posted by cmbe92guy

The swap is mechanically done. No leaks. Completed the transmission fill procedure after school today. Trans shifts smoothly through PRND/M1/M2 on stands. Next step is to attach the front D shaft and button up the underside. Also need to permanently mount the oil cooler using the factory crash bar studs. I’m going to do a few more runs up to temp before I set the car down. On the road soon!

Could you use the 335is cooler for the trans? It would offer OEM fitment. Obviously not AN style fitting and I don't know squat about autos.

[cmbe92guy]

Originally Posted by TyroneShoelaces

Could you use the 335is cooler for the trans? It would offer OEM fitment. Obviously not AN style fitting and I don't know squat about autos.

You could adapt the factory E series trans cooler lines to fit the 8hp. However, 6hps/DCTs run substantially hotter than the 8hp. This introduces an overcooling issue that decreases the longevity of the trans. Also, if you’re referring to the cooler that sits in the L wheel well on -is cars, that is an auxiliary radiator for coolant. It plumbs into the upper radiator hose and is not compatible with OEM trans cooler lines/components. That being said, I’m sure there’s a way to make it work. But it would involve bending/repurposing OEM lines in a way that is unsafe & causing overcooling issues.

[cmbe92guy]

First drive is complete. Can confirm: the 8hp on stock tune is miles better than the 6hp on XHP stg 3. Not even close.
Some things I’ve got to tidy up:
- Make a better cooler mount. I’m not a fab guy lol.
- An AN fitting near the cooler adapter in the trans tunnel is slowly leaking. Not looking forward to removing the front driveshaft yet again.
- The instrument cluster shows the car to be in Park 24/7. I’ve been monitoring the transmission via the CANTCU configurator. The cluster needs to be updated to best communicate well with the CANTCU.
- I’m getting a persistent PTCAN code triggering a CEL. No drivability issues present. Will ask Kenneth about that.
- Need to perform the Diff ratio adaptation procedure.
- Need to mount the CANTCU neatly in the glovebox. Also need to fab a shifter cover to remove the unsightly, gaping hole in my center console.

[colorado.e9x]

Hear me out: DCT shifter surround. Program the Sport button to a more aggressive map. OEM+

[cmbe92guy]

[QUOTE="colorado.e9x;30882155"]Hear me out: DCT shifter surround. Program the Sport button to a more aggressive map. OEM+

I like the idea. Not sure about the shifter surround/button by itself but e9x non-m dct shifters are like $400 in crappy condition.

[Keystonezzzzz]

@cmbe92guy Hey! I’m also having a similar issue with my 8hp swap and i was wondering if you also had faults in other modules i got fault codes for PT-Can in a couple of modules and it all started after the trans swap but the car drives perfectly fine. I’m trying to see where i might have went wrong or if i need to recode something etc.

[cmbe92guy]

[QUOTE=Keystonezzzzz;30887122]@cmbe92guy Hey! I’m also having a similar issue with my 8hp swap and i was wondering if you also had faults in other modules i got fault codes for PT-Can in a couple of modules and it all started after the trans swap but the car drives perfectly fine. I’m trying to see where i might have went wrong or if i need to recode something etc.

I have not had a chance to scan other modules yet (I’ve been using MHD to monitor DME codes). I wouldn’t be surprised if I had PT-CAN related errors in other modules. I’m going to email CANTCU support about it tonight. Are you also using CANTCU or are you on another controller?

[Keystonezzzzz]

cmbe92guy Also Using a cantcu controller, and a 8Hp45x outve a 2016 M235i xdrive. Had the issue since i put it on just kinda ignored it because it didn’t seem to cause issues. until i scanned other modules and then i was like YUP gonna just let that simmer till i figure it out 😅Did u happen to get your paddle shifters working? also my car is a 2013 335i