Another 8HP45 swap for an E90 335xi

[V8bait]

There's a bunch of these nowadays it seems so just wanted to put together a quick udated TLR post for some random info and little bits I found out as I completed the swap. Instructions for CanTCU are pretty detailed already but this may help anybody doing the swap themselves. Overall difficulty was not bad, doable on the ground with tall jack stands.

Receiving car:
2008 335xi, ported head, FBO w/ inlets/hotpipes, Walboro 535 drop in, cheap 17T chinesium tubofans, full E85 on stock TMAP ~530awhp

Donor car:
Some N55 x-drive car with 60k miles and a 8hp45

Controller: CanTCU from M33 Performance and I want to add this place was GREAT, owner is great to work with if you need something

Things that may help to know about the swap:

Physical differences:
- Donor car MUST be N55
- N55 torque converter bolts to older N54 flexplate
- For X-Drive, you swap the 6HP tcase to the 8HP trans and you're good to go, everything bolts over
**N20 8HP trans is 1" longer, at least for X-Drive, and while you can physically mate them (by drilling out one hole) you need the N55 converter anyway, and the trans is physically too long. (Thank you Josh from Guru Autowerks for confirmation) N55 donor or bust.

Trans cooler differences:
- 8HP are larger diameter, need adapter
- 8HP lines are plastic, trash, 6HP lines are aluminum, good
- If you want to keep OEM 6HP trans cooler you can, I got an 8HP adapter for -8AN, and got some 8AN male flare to 1/2 hose barb adapters from amazon, cut the 6HP lines to just a little shorter, and used a 12mm line flare tool (hard to find 12mm but they are available on Amazon). File smooth and slip some oil line over them and clamp away, done.
- 6HP trans cooler is fine for 8HP despite what people may say, unless you are doing motorsports, in which case it was never good enough to begin with.

Wiring:
- Can re-use 12v from 6HP harness and PTCAN from 6HP harness and route into the car (I removed the entire factory harness and rolled it into the DME box, de-pinned the 3 wires I wanted for 12v, PTCAN high/lo, and routed them into the glovebox)
- E series DCT shifter assembly from 335is bolts right up to the console like factory

Coding:
- CanTCU can use the built in "flasher" to remove the immobilizer
- For coding CanTCU wiki says to code the vehivle order to automatic S205A, for anybody using ProTools on your phone where you can't see the numbers, this is "automatic", not "steptronic" that you probably start with factory. Does it matter? No idea, but I coded to "Automatic" because CanTCU told me to.
- The E90 dash will display all 8 gears once swap is complete, and even the proper picture for the shifter, because magic.

Tuning:
- If you're running N20 TMAP >22psi then your reported torque values will be off. You can either increase them in the CanTCU setup by a percentage or retune the car
- MSD80/81 has a maximum torque it will send that is lower than the 8HP maximum as far as I know, so even if you raise the torque tables you probably should still increase the torque in CanTCU some, unless you are running pump gas near stock, then just leave it alone.
- Make sure you do not disable torque interventions w/ ignition in the tune, basically- tune it or have your tuner set it up like a 335is/1M DCT trans.

10/10 would swap again.

 

[doublespaces]

Can someone get me up to speed on the benefits here? Faster shifting? Isn't there an aftermarket for increasing the torque handling capacity?

 

[V8bait]

In my case my 6 speed was more of a 5 speed with 5th failing and slipping even at low throttle.

There's a lot of reasons. Good 6hp boxes are hard to find as they're all old. They don't handle much power. They are kinda meh.

The 8hp handles around 100 more torque than the 6hp (6hp will fail over 500, 8hp can do 600 pretty solid), has better gearing, better shifting, is cheap and easiest to find good used boxes and when you do you can have more confidence they aren't garbage already.

 

[SLOWESTN54]

In my case my 6 speed was more of a 5 speed with 5th failing and slipping even at low throttle.

There's a lot of reasons. Good 6hp boxes are hard to find as they're all old. They don't handle much power. They are kinda meh.

The 8hp handles around 100 more torque than the 6hp (6hp will fail over 500, 8hp can do 600 pretty solid), has better gearing, better shifting, is cheap and easiest to find good used boxes and when you do you can have more confidence they aren't garbage already.

how much would you say overall the swap costs excluding transmission.

 

[Traf]

Great shit !

 

[V8bait]

how much would you say overall the swap costs excluding transmission.

CanTCU was $1200 iirc
8hp line adapter was $90 I think there's cheaper ones
-8AN to 1/2" barb fittings were $10 on Amazon just checked
Aluminum transmission pan ~$100
Transmission fluid ~$75 (I used Valvoline max life atf)
Needed a 12mm flare tool which was hard to find $70
335is shifter $250 on eBay w/ trim
Trans was $350 w/ 60k

Probably around $1800 without transmission. The controller was the most expensive part. So, cheaper than a rebuild, but more expensive than slapping in a 6hp.

 

[SLOWESTN54]

CanTCU was $1200 iirc
8hp line adapter was $90 I think there's cheaper ones
-8AN to 1/2" barb fittings were $10 on Amazon just checked
Aluminum transmission pan ~$100
Transmission fluid ~$75 (I used Valvoline max life atf)
Needed a 12mm flare tool which was hard to find $70
335is shifter $250 on eBay w/ trim
Trans was $350 w/ 60k

Probably around $1800 without transmission. The controller was the most expensive part. So, cheaper than a rebuild, but more expensive than slapping in a 6hp.

Appreciate the information, Also I know Bms sells a complete trans cooler kit for a 8 speed 340i. I wonder if you could make it work in E chassis.

 

[V8bait]

Appreciate the information, Also I know Bms sells a complete trans cooler kit for a 8 speed 340i. I wonder if you could make it work in E chassis.

Just use a 6hp cooler kit with 8AN and the adapter, I just wanted to keep things near stock on this particular car.