[Shemeshhj]

Hi everyone and Happy New Year!
I drive a single turbo (6266) e92 335xi fitted with the infamously sluggish zf6hp19 6-speed auto that can't hold power, and it's slipping with only 18psi. Instead of doing a rebuild or swapping to a manual (it's my daily and I live in busy NYC) I thought of doing a zf8hp45 swap from an e84 x1.
I can't confirm this, but it seems that the e90 and the e84 are essentially the same chassis, the e84 just having an suv body sitting on it. I came across a thread where this swap was discussed in Australia in early 2018 but they never followed up in regards to whether it worked or not.
This swap would be a great solution as the zf6 is rated to hold 295ftlb but people report them starting to slip only around 450ftlb, so applying the same 50% increase to the zf8hp45's claimed limit of 450ftlb (ZF's claim) would mean that in practice it can hold up to approx. 675ftlb.

Here is what a week's worth of research revealed:
- zf6hp19 and zf8hp45's bell housing are identical
- e92 & e84 driveshafts (front and rear) are identical, same part #
- e92 & e84 torque converters are identical, same part #
- e92 & e84 CAN control unit is identical, same part #
- e92 & e84 TCUs are identical, same part #
- Zf8's are VIN locked, which may present an issue. A tuning company I spoke to said it should not be too difficult to get around that

I spoke to xHP about this project and they said that since the zf8 is VIN locked, it communicates with the FEM and the DME before starting to operate, saying this swap would require a different CANBUS architecture.

I would love to get your insight on this project, I am pretty set on making this happen but my knowledge of electrical vehicular communications and how that sort of stuff works is very limited. I'll be posting this thread on the other forums as well. All feedback would be really appreciated.

**Please don't suggest a manual swap; it makes no sense to manual swap a car that is rolled off the assembly line with a manual...**

[DR-JEKL]

DCT swap?

[feuer]

It didn't make much sense to ST an 335 xDrive and you did it anyways. So whatever people suggest should be considered.

[88atlas07]

This would be a pretty cool swap. I have the zf8 in my '14 535i and its a superior trans to the 6hp in every way

[JuniorB]

The hardware is the easy part, the software on the other hand....".

[MILLER335I]

Did anyone ever do this swap?

[nyt]

There's a 6hp28 adapter and kit on the market shortly. That's probably the best bet.

spool street /threads/guru-autowerks-zf-6hp26-28-transmission-adapter.7107/

The 8hp70 was available on an n55, so you can find some with matching bell housings. You'll need an aftermarket tcu. HTG Tuning makes one, they call it a GCU (gearbox control unit).

Some active hybrid models had an N55 and an 8hp70. Here's an example. They're not hard to find at the moment. Pretty certain a new driveshaft will be needed as well.

https://www.ebay.com/itm/13-15-OEM-B...Z/224157261422

The 8hp45 swap would be stupid, especially with 8hp70 available. And not all the bell housings are the same.

[southbaysteve]

I love when someone says its a stupid idea to do something that I've been researching and discussing with experts in the aftermarket for nearly a year. I vehemently disagree, but I will be tactful when responding. My main point is that it is not a stupid idea to consider the 8HP45 to be used in place of the 6HP21 transmission. the 8HP45 makes a bunch more sense than the 6HP28 (from the diesel models). It makes incredibly more sense than the 8HP70 or 75 versions based on cost alone. It's a purely logical, more technically advanced and time efficient modification that few have attempted to date, but more may consider in the near future. However, as the author rightly pointed out, an HTG GCU transmission adaptation system is a requirement for any upgraded automatic transmission in the E90 platform due to the way BMW made transmissions VIN locked after the 6HP versions. I get it you might want to do this VIN locking thing, but then again, I don't get it. Its like locking up the snack foods in the office at work.

First of all, don't rely on the relative capabilities (rating) of the transmission's designation for torque and clamping force, and expect to exceed it's intended stock rating routinely. Your donor transmission might have been beat a lot so the gears, clutches and so on might be nearing the end of life. Expecting more is gambling. The ability to lock up without slipping well beyond the stock ratings of the transmission is relying on statistical probability to get home. It "should" work if you're not beating on your car all the time, but if you're doing hard pulls, off the line starts, using the transmission harder than intended, and have not upgraded things like cooling, clutches, and other internals, it'll eventually fail when you least expect it, catastrophically. Like the N54 engine, whatever transmission you select, get it fully serviced by a reputable BMW transmission specialist before you drop the 6HP21 and shove it to the corner. It'll be money well spent, not figuring out what broke later.

As the thread author rightly stated, the housing, the dimensions, the converter, the drive shaft, and the mount points are identical between the 8HP45 and the 6HP21. The 8HP45 weight is slightly more (2 extra gears, solenoids in the mechatronics, etc.) but all else is very similar. However, he also rightly stated that, the 8HP series was CMOS encoded in the TCU and the mechatronics to be VIN specific. Meh. But there is a work around for this. And it turns out that this work around has more advantages than tradeoffs for the trouble.

The physical 8HP45 transmission and torque converter can be swapped into the E90/N54 RWD chassis, relatively easily. It's a simple one for one, and it'll seem to 'drop' into place based on the physical similarities. The 8HP45 can be (must be) adapted for use in the E90 with the use of the HTG GCU and software (along with some small wiring changes inside the transmission). It, the HTG GCU is completely bypassing the VIN locked TCU (thanks BMW, for nothing) and the HTG unit offers a crap-ton of programmable options that can't be done on a stock transmission. You can dial up shift response times for the track and dial it back down for the drive home, per their marketecture website. Even a synthetic clutch kick... in a frickin' automatic transmission, if you're into hooning your car. Frankly, I know others are using this with other ZF produced transmissions on the track, so I know I can get it to work, in time. I'm not done yet, just buying parts now. so I'll record and post on YT as well as take some stills for here, maybe a new thread.

You can find out about the GCU (TCU bypass) here --> htg-tuning DOT com

Additionally, the 8HP45 can (should) be significantly reinforced for heavier duty use by companies such as Pure Drivetrain Solutions. Their work is good. It's not cheap, but it's durable. Is a Stage One 1000HP, 850FT-LB torque rebuild enough to cover pretty much any N54 powered car on the road to date? Uh, ya. If you're planning 17, 19T twins or a big single turbo, you need more transmission clamping power when the snails starts screaming.

There are some re-wiring things that need to be in place too. You'll need to bypass the TCU and still communicate with the ECU and that's where another company's parts come in. I found them looking for a replacement for my welded open differential (again, thanks for nothing BMW; you coulda just passed the insignificant cost off to us customers for a real LSD, but no...)

I am going to work on the adaptations with the fine folks from Seems Legit Garage and see what happens. go here... seemslegitgarage DOT com /product-page/8hp-harness-kit

Apparently, you'll need 2 parts; the solder-in terminal connection printed circuit board inside of the mechtronics in the donor 8HP45, which jumpers the correct pins to bypass the BMW TCU, and the 8HP harness kit. This harness simplifies the installation of the physical components into the transmission bypassing the TCU which usually connects by the main plug, which connects the TCU to the mechatronics. Both sold ready to use by Seems Legit Garage. Full install instructions on their website.

This 8HP45 transmission swap makes more sense that trying to find a 8HP70 or 75 candidate transmission, shove an 8HP7x bigger body into the E90 chassis, do custom mount points, driveshaft and adaptor plate work and so on, as well as the same TCU bypass requirements of the 45... and the 45's are a bunch less money on ebay right now ($700-800) than the 70 or 75s ($1300-2500 IF you can find the right one, right generation, correct gearing, etc).

So... No, it's not a stupid idea to swap the 8HP45 for the 6HP21.

Originally Posted by nyt

There's a 6hp28 adapter and kit on the market shortly. That's probably the best bet.

spool street /threads/guru-autowerks-zf-6hp26-28-transmission-adapter.7107/

The 8hp70 was available on an n55, so you can find some with matching bell housings. You'll need an aftermarket tcu. HTG Tuning makes one, they call it a GCU (gearbox control unit).

Some active hybrid models had an N55 and an 8hp70. Here's an example. They're not hard to find at the moment. Pretty certain a new driveshaft will be needed as well.

https://www.ebay.com/itm/13-15-OEM-B...Z/224157261422

The 8hp45 swap would be stupid, especially with 8hp70 available. And not all the bell housings are the same.

[nyt]

Originally Posted by southbaysteve

8hp70s were avail for like a grand when I looked. Even if now it's 1300 as you say, you're saving what, 500-600, but linked a $1200 cable, a $1200 controller, and mention a $6000 rebuild? ok.

You don't need an adapter plate if you get an 8hp70 from an active hybrid as mentioned. Same bell housing, bolts right up.

6hp28 is still the way to go, imo. The cost is much lower, kits are readily available, they're supported by xhp, and they can hold more torque.

Please post back once you have some progress. I'm interested to see how that comes out and how much longer it takes.

[southbaysteve]

Originally Posted by nyt

8hp70s were avail for like a grand when I looked. Even if now it's 1300 as you say, you're saving what, 500-600, but linked a $1200 cable, a $1200 controller, and mention a $6000 rebuild? ok.

You don't need an adapter plate if you get an 8hp70 from an active hybrid as mentioned. Same bell housing, bolts right up.

6hp28 is still the way to go, imo. The cost is much lower, kits are readily available, they're supported by xhp, and they can hold more torque.

Please post back once you have some progress. I'm interested to see how that comes out and how much longer it takes.

Hi NYT, Thank you for responding and not flaming me. I appreciate your points, and I wish I had your luck in finding a reasonably priced, inline 6, non-"x" BMW version 8HP70 that could be a donor for my E90.

For reference, the 8HP70 came in the BMW F01/F02 (both v8 cars), the F10/11 (a few of those were 5 series N55 powered, so no adaptor plate needed), the X5 50i (v8 powered), and the F30 (320d and 335d).

Naturally, that trans (8HP70) could hold more torque natively, if it was in great shape before installing it. In my experience, once they're in the recycler yard, they're good candidates to rebuild but not just re-install. There are low mileage good ones out there, but most of the transmission guides I've read say at the least, an intensive service is called for, if not a full clutch and ring pack, but again, not stating this is always the case.

You made one more good point, that the 6HP26 from the 335d would make a drop in transmission swap, and you're correct. The 6HP26 is a good fit, however its from a diesel motor with a different gearing profile than a gasoline engine so the logic of this transmission is intended for shorter shifts of the much more torque of a diesel motor. Just a consideration, not a statement that it cannot or should not be used.

The 6HP26 has 6 gears (and reverse), but the 8HP45 has 8 forward gears, and better, crisper shifts than the older 6HP26, with really no gains in size or physical connections to the chassis than the 6HP21 or 26.

The reason I am building the transmission out by using Pure Drivetrain Solutions (or, any true performance transmission shop that knows the ZF transmissions well) is that all of the internals are improved (gates, rings, valving, clutchpacks, baskets, planetaries, etc.) so it's not operating on the edge of it's clamping capability connected to a 600-650HP single turbo motor with an LSD behind it.
Consider the cost of building the go-fast parts (most of the guys on here are building out for go-fast, turbos, single turbo, additional fueling, better flow, etc.) and 'most' AT car guys will not look so excited at the (cost, time, new knowledge, etc.) buildout of the transmission (except the 6MT guys with 2 stage clutches and so on), so they attempt to buy the next stronger transmission version and use it with little to no modification or reinforcement.

I get it. But I also hate having to take out a transmission twice or 3 (or more) times because gears slip when pushed beyond their designed limits often. I'd rather drive the car or work on something else than a subsystem I just reinstalled. So, plan on and spend the $4K on the transmission and torque converter build for Stage 0 or $7K for Stage 1. It's like building the bottom end of the engine. You're only building it so you rely on the parts in that subsystem when they're gonna be pushed harder than fast commuting, often, and don't want to have to do time consuming procedures on the car often.

Also, for me, it's my preference because its not as common to use a lower 8HP transmission to support a higher power build, and the 8HP45 is very common in the correct version that would be a more direct fit for use in my situation.

As you stated, i need to show some work on this. I agree. Typing is easy, and turning wrenches and spending several thousand dollars over the Christmas season on car parts..well, that's harder to do.

Merry Christmas, Mr. NYT.

[nyt]

Originally Posted by southbaysteve

Hi NYT, Thank you for responding and not flaming me. I appreciate your points, and I wish I had your luck in finding a reasonably priced, inline 6, non-"x" BMW version 8HP70 that could be a donor for my E90.

For reference, the 8HP70 came in the BMW F01/F02 (both v8 cars), the F10/11 (a few of those were 5 series N55 powered, so no adaptor plate needed), the X5 50i (v8 powered), and the F30 (320d and 335d).

Naturally, that trans (8HP70) could hold more torque natively, if it was in great shape before installing it. In my experience, once they're in the recycler yard, they're good candidates to rebuild but not just re-install. There are low mileage good ones out there, but most of the transmission guides I've read say at the least, an intensive service is called for, if not a full clutch and ring pack, but again, not stating this is always the case.

You made one more good point, that the 6HP26 from the 335d would make a drop in transmission swap, and you're correct. The 6HP26 is a good fit, however its from a diesel motor with a different gearing profile than a gasoline engine so the logic of this transmission is intended for shorter shifts of the much more torque of a diesel motor. Just a consideration, not a statement that it cannot or should not be used.

The 6HP26 has 6 gears (and reverse), but the 8HP45 has 8 forward gears, and better, crisper shifts than the older 6HP26, with really no gains in size or physical connections to the chassis than the 6HP21 or 26.

The reason I am building the transmission out by using Pure Drivetrain Solutions (or, any true performance transmission shop that knows the ZF transmissions well) is that all of the internals are improved (gates, rings, valving, clutchpacks, baskets, planetaries, etc.) so it's not operating on the edge of it's clamping capability connected to a 600-650HP single turbo motor with an LSD behind it.
Consider the cost of building the go-fast parts (most of the guys on here are building out for go-fast, turbos, single turbo, additional fueling, better flow, etc.) and 'most' AT car guys will not look so excited at the (cost, time, new knowledge, etc.) buildout of the transmission (except the 6MT guys with 2 stage clutches and so on), so they attempt to buy the next stronger transmission version and use it with little to no modification or reinforcement.

I get it. But I also hate having to take out a transmission twice or 3 (or more) times because gears slip when pushed beyond their designed limits often. I'd rather drive the car or work on something else than a subsystem I just reinstalled. So, plan on and spend the $4K on the transmission and torque converter build for Stage 0 or $7K for Stage 1. It's like building the bottom end of the engine. You're only building it so you rely on the parts in that subsystem when they're gonna be pushed harder than fast commuting, often, and don't want to have to do time consuming procedures on the car often.

Also, for me, it's my preference because its not as common to use a lower 8HP transmission to support a higher power build, and the 8HP45 is very common in the correct version that would be a more direct fit for use in my situation.

As you stated, i need to show some work on this. I agree. Typing is easy, and turning wrenches and spending several thousand dollars over the Christmas season on car parts..well, that's harder to do.

Merry Christmas, Mr. NYT.

Just a note, the 6hp26/28 isn't drop in, needs an adapter plate, but the guru kit is minimal effort to install.

The gearing is also identical to the 6hp21

I built my 6hp21 myself with billet parts and all the bells and whistles, however the 6hp28 option wasn't available when I did. If I break this transmission (so far so good) it's getting replaced with a 6hp28.


https://spool street/threads/guru-au...07/post-106512

[southbaysteve]

Originally Posted by nyt

Just a note, the 6hp26/28 isn't drop in, needs an adapter plate, but the guru kit is minimal effort to install.

The gearing is also identical to the 6hp21

I built my 6hp21 myself with billet parts and all the bells and whistles, however the 6hp28 option wasn't available when I did. If I break this transmission (so far so good) it's getting replaced with a 6hp28.


https://spool street/threads/guru-au...07/post-106512

Thank you about the 6hp28, which I visually estimated based on what I saw in a diagram, is not a bolt to bolt match for 6hp21 equipped N54 cars.. Sorry for the mis-information on that, and the gearing differences, which again estimates from same diagram of the 6hp28 visually, not in a table that should have been referenced.

What I think is very cool is that you rebuilt the 6hp21 yourself. Most people don't have the expertise tools and risk tolerance to do this. I don't (so I am outsourcing to a transmission company for the 8hp45 and the TC upgrades).

As promised, I will not post a ton to this thread until I have something more tangible to contribute than just an opinion... I think that is only fair.
In case I didn't mention it, Merry Christmas.
-Steve

[N55Jamaican]

I am about to dive into a Transmission swap and need some help. I have a 2011 E90 335i sedan. My question is, will the 8hp70 from a 10-12 F12 fit 650i bolt up under my E90 chassis with out cutting?

[JLFC]

Originally Posted by N55Jamaican

I am about to dive into a Transmission swap and need some help. I have a 2011 E90 335i sedan. My question is, will the 8hp70 from a 10-12 F12 fit 650i bolt up under my E90 chassis with out cutting?

I’m also flirting with the idea of a transmission swap, same car BTW.

Ideally, a Manual swap would be the coolest, but in my country it is almost impossible to find one, and VERY expensive to buy from abroad.

So I’m left with two options:

1 - DCT. The idea of swapping a DCT into my car is very appealing, as it is a very capable and sporty transmission, but it is quite expensive to buy and maintain.

2 - ZF8. The ZF8 is an AMAZING transmission, and I can get my hands on one for a relatively low amount of money as it is very abundant. Those insanely crisp, ignition-cut shifts have my whole heart! It is such a “dual personality” transmission! It can be very smooth and comfortable when needed, but also very crisp, and quite sporty.
So, the hardware seems quite easy to get done, but the software is the key problem, so cost might get very close, if not surpass the cost of a DCT swap (due to where I live, mostly).

So, I would very much like to tackle a ZF8 swap, and would really like to make it work natively, if there is somehow a way to work around that VIN lock stupidity. However, the idea of a “plug n’ play” DCT swap (2011 E90 N55) is also very interesting.

I’ll eventually update this thread with any findings or ideas that I may come across, and I would also very much appreciate any sort of information from the community.

Looking forward to swap my ZF6 for a much more capable and enjoyable transmission.

JL

[N55Jamaican]

Originally Posted by JLFC

I’m also flirting with the idea of a transmission swap, same car BTW.

Ideally, a Manual swap would be the coolest, but in my country it is almost impossible to find one, and VERY expensive to buy from abroad.

So I’m left with two options:

1 - DCT. The idea of swapping a DCT into my car is very appealing, as it is a very capable and sporty transmission, but it is quite expensive to buy and maintain.

2 - ZF8. The ZF8 is an AMAZING transmission, and I can get my hands on one for a relatively low amount of money as it is very abundant. Those insanely crisp, ignition-cut shifts have my whole heart! It is such a “dual personality” transmission! It can be very smooth and comfortable when needed, but also very crisp, and quite sporty.
So, the hardware seems quite easy to get done, but the software is the key problem, so cost might get very close, if not surpass the cost of a DCT swap (due to where I live, mostly).

So, I would very much like to tackle a ZF8 swap, and would really like to make it work natively, if there is somehow a way to work around that VIN lock stupidity. However, the idea of a “plug n’ play” DCT swap (2011 E90 N55) is also very interesting.

I’ll eventually update this thread with any findings or ideas that I may come across, and I would also very much appreciate any sort of information from the community.

Looking forward to swap my ZF6 for a much more capable and enjoyable transmission.

JL

The guys over at CAN Performance Engineering can help with the software/ VIN locked situation. Plug an play sort of.

In theory based on my google search the 8HP has 2 more gears than 6HP, the dimensions have remained the same while the weight has been reduced by as much as 3%. It now weighs 87 kg with a mid-size 8HP70 transmission including oil. So a donor F series 8HP 45/70/90 may fit under the E series chassis. I plan to purchase the CANTCU and a great stand alone ECU (MaxxECU) to mate with it. Then I can move forward with my swap project.

[cmbe92guy]

In the midst of an 8hp45 swap using the CANTCU. Virtually plug and play.