PROMO Guru Autowerks - ZF 6HP26/28 Transmission Adapter

SlowE93

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Jul 2, 2017
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RWD can use the 6HP21 or 6HP28 #063 valve body and yes the EGS from diesel transmission.

All said and done not including labor you're looking at about $3500USD. This includes every single item needed to complete the installation; adapter kit, donor trans, Adrenaline fluid, new zf pan/filter/seals, EGS coding, custom trans tune, cooler lines etc.

Contact me directly we can chat in depth.
This is assuming the donor trans is in good shape and not have any internal issues, correct ?
For peace of mind, I would like to have a freshly rebuilt trans before going through all the trouble of conversion.
What would that expect to be tacked on to the bill ?
My other question is....what causes a trans to not upshift under WOT and more power than stock ?
I have seen this on youtube videos of cars on the track and street racing from a dig.
A couple cars come to mind. A twin turbo c8 vette and a camaro ZL1. My car has also done this if boost is not limited far down enough in 2nd gear.
I ask because I would hate to go thru the trouble of swapping and still have some existing issues.
Not sure what trans is in the C8 or the Zl1.
 
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SlowE93

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The C8 uses a Tremac DCT and a ZL1 at least the new one had a 10R80 i believe
So what causes these cars and my SlowE93 to not upshift when using full power ?
My car has done it (not always) from 2nd to 3rd
The Zl1 did it from same gear I believe.
The C8 I think did it from 1st to 2nd, or same 2nd to 3rd shift.
Keep in mind, I run xHP as well.
Before xHP was even around, on Alpina flash my car would do this but from 1st to 2nd.
It NEVER did it on factory software.
I keep boost lower now in 2nd and so far so good. When boost was higher, it would do it once in a great while.
Anyways, as I said, would hate to swap trans and still have these crappy issues that others also experience when running higher power.
 

SLOWESTN54

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Feb 9, 2021
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So what causes these cars and my SlowE93 to not upshift when using full power ?
My car has done it (not always) from 2nd to 3rd
The Zl1 did it from same gear I believe.
The C8 I think did it from 1st to 2nd, or same 2nd to 3rd shift.
Keep in mind, I run xHP as well.
Before xHP was even around, on Alpina flash my car would do this but from 1st to 2nd.
It NEVER did it on factory software.
I keep boost lower now in 2nd and so far so good. When boost was higher, it would do it once in a great while.
Anyways, as I said, would hate to swap trans and still have these crappy issues that others also experience when running higher power.
With the C8 It was a ECU/TCU issue where the ecu wouldn't pull enough power out to allow the trans to shift. With the lack of tuning they were having issues with torque reduction pre shift. Are you using the newest revision (V1.7)? Any error codes in XHP? Maybe play around with the torque reduction slider for 2-3?
 

SlowE93

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With the C8 It was a ECU/TCU issue where the ecu wouldn't pull enough power out to allow the trans to shift. With the lack of tuning they were having issues with torque reduction pre shift. Are you using the newest revision (V1.7)? Any error codes in XHP? Maybe play around with the torque reduction slider for 2-3?
Never any errors.
Yes I always update whenever xHP updates.
Never messed around with torque reduction. Only shift speeds and rev match.
I will end this here since I dont want to further derail this thread.
Thank you for the replies though.
 

nyt

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Sep 15, 2019
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I wish I knew of this option a couple of months ago. My friend owns a transmission shop and even with him being VERY generous I spent over $7,000 and a month in hell. Against my friends strong recommendation I had my spare 6HP21 rebuilt with Precision Raceworks Kolene coated frictions that never shifted right, made noises and harshly clunked into drive. Then I made the mistake of buying a used 6HP21 that had been rebuilt with the same "racing frictions" that turned out to be already ruined by the prior owner. Finally my friend felt sorry for me, and offered free labor to rebuild my first transmission again with regular stock parts. The car drives great now and I am using XHP. But I KNOW with increased power my stock trans probably won't last too long. When that day comes soon, it looks like this is definitely the right option for me. This seems like the perfect solution. $3,500 is pretty cheap to have a OEM style solution to handle power. Trying to modify something that is not designed for high HP will never beat the reliability of a bigger transmission that was already designed to take that power. I guess you will be hearing from me eventually. I have already destroyed one differential and transmission so far.

I'm using those same frictions and steels (which are produced by Alto) and xhp stage 3. There is no problem with them. They shift and operate great. Are you using the correct trans fluid? Did you reset your adaptations? Did your builder botch something?
 
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SlowE93

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I'm using those same frictions and steels (which are produced by Alto) and xhp stage 3. There is no problem with them. They shift and operate great. Are you using the correct trans fluid? Did you reset your adaptations? Did your builder botch something?
Wanna build me a trans as a side project ?
Lmk how much.
 

nyt

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Sep 15, 2019
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Wanna build me a trans as a side project ?
Lmk how much.

It's more expensive than the 6hp28 route, which wasn't as easy of an option when I built mine. Without an upgraded input and intermediate shaft, only made by Nizpro in .AU, you'll run into issues somewhere around 800hp. IIRC, the shafts alone were almost $2500. 6hp28 is definitely the better option.

Unless you were talking about building a 6hp28.... Either way, I just moved and it will be ~6-8 months until my shop is built :(
 

vonhassen

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Dec 4, 2019
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I stand corrected, yes Caleb is the first 5 series! Luckily for him it uses the same AWD transfer case mount as the 335xi and he already has E-Shift setup so the donor X5 transmission doesnt need to be converted to M-Shift. The RWD 535i kits will require a different transmission mount bracket and they will have to convert their donor transmissions from M-Shift to E-Shift... or convert vehicle to M-Shift.
Hey any update on the XI and/or 535xi guys? My buddy has been sitting on a set of PD clutches & has a spare low mileage 6hp21/26 sitting around. its been like a year since he got it & hype/progress has died down, so I am waiting for the right moment to introduce him to this whole swap :)

He has slowed down on turning everything up, but I suspect its the 5th gear onward shift flares that is the reason why.
 
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GuruAutowerks

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Nov 26, 2020
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Thank you to everyone that comes in here to ask questions and support us... my apologies for the delay replying. Things are crazy right now in a good way!

I wish I knew of this option a couple of months ago. My friend owns a transmission shop and even with him being VERY generous I spent over $7,000 and a month in hell. Against my friends strong recommendation I had my spare 6HP21 rebuilt with Precision Raceworks Kolene coated frictions that never shifted right, made noises and harshly clunked into drive. Then I made the mistake of buying a used 6HP21 that had been rebuilt with the same "racing frictions" that turned out to be already ruined by the prior owner. Finally my friend felt sorry for me, and offered free labor to rebuild my first transmission again with regular stock parts. The car drives great now and I am using XHP. But I KNOW with increased power my stock trans probably won't last too long. When that day comes soon, it looks like this is definitely the right option for me. This seems like the perfect solution. $3,500 is pretty cheap to have a OEM style solution to handle power. Trying to modify something that is not designed for high HP will never beat the reliability of a bigger transmission that was already designed to take that power. I guess you will be hearing from me eventually. I have already destroyed one differential and transmission so far.

I appreciate you sharing your experience, it always pains me to hear horror stories like. Anyone whos played with cars enough knows what its like to be in those grueling situations. Glad you finally got it back together, you have a damn good friend there... sounds like he went above and beyond. I sincerely wish your current setup nothing but a long life with 0 issues but if the time comes I would love to help. You're spot on about modify something with a lower rating VS starting with a bigger transmission designed for the task at hand. Good luck out there and have fun!

This is assuming the donor trans is in good shape and not have any internal issues, correct ?
For peace of mind, I would like to have a freshly rebuilt trans before going through all the trouble of conversion.
What would that expect to be tacked on to the bill ?
My other question is....what causes a trans to not upshift under WOT and more power than stock ?
I have seen this on youtube videos of cars on the track and street racing from a dig.
A couple cars come to mind. A twin turbo c8 vette and a camaro ZL1. My car has also done this if boost is not limited far down enough in 2nd gear.
I ask because I would hate to go thru the trouble of swapping and still have some existing issues.
Not sure what trans is in the C8 or the Zl1.

Yes for sure, the pricing is for a stock used transmission in good shape... obviously there is risk present when buying used parts. So far nobody has chosen to rebuild the transmissions and everyone is running a stock setup with fresh seals/fluid. I do have future customers that are going to be doing full rebuilds though and thats obviously the preferred path for builds that arent budgeted as tight. Many customers that already have stock 6HP28s installed are planning on buying another core for a proper rebuild since theyre affordable (especially 100k miles +). I try to be upfront with all of my customers that nothing is bullet proof, anything can break and 110% someone will break one of these transmissions eventually. I like to inform them about the biggest weakpoint that all ZFs share, the bronze bushings and the best way to minimize that risk is good fluid/cooler setup for heat management. I also give information and quotes on full rebuilds with upgraded bushings, clutch packs, welded/machined e clutch basket, higher pressure valve body and performance stall options.


Below are several ways we minimize risk when sourcing a used transmission. I consult and help every customer with this process, many times making phone calls or talking with the yards, checking VINs etc and working directly with the customer or installer.

- Proper homework on donor transmission is essential. VIN check of donor transmission goes a long way in ensuring the transmission mileage advertised is accurate. Sometimes you can also see vehicle maintenance history to see how the donor vehicle was taken care of.

- I also recommend talking to the sellers by phone, feeling them out goes a long way. Its also a good time to ask questions about the transmission, such as estimated donor transmission pull/removal date, any visible damage to the unit or possible flood/fire damage, return policy/warranty, shipping options etc.

- Accumulate a list of transmission prospects, do proper homework on them... choose your best/gut instinct base on the data youve learned.

- We also recommend never buying the transmission early. Its better to make sure its puchased AND installed within the return policy window. That way if you do have an issue on your first drive it can be returned within the 30 to 90 days return window. Local purchases are obviously easier to return to and when possible I try to have customers pickup local transmissions. Its nice to inspect in person and have no hassle/no shipping cost returns. That said there are some smoking deals online and across the country that have turned out very well but homework is even more essential when youre buying something sight unseen.


As for your question about not upshifting under WOT with more power than stock... I honestly cant comment too much on that as it would just be speculation. Things like that have a lot of variables though from tuning to transmission internals and capabilities. I can so we have no seen any type of upshifting issues on the transmission with the test kits that are on the road or during prototype testing.

I'm using those same frictions and steels (which are produced by Alto) and xhp stage 3. There is no problem with them. They shift and operate great. Are you using the correct trans fluid? Did you reset your adaptations? Did your builder botch something?
It's more expensive than the 6hp28 route, which wasn't as easy of an option when I built mine. Without an upgraded input and intermediate shaft, only made by Nizpro in .AU, you'll run into issues somewhere around 800hp. IIRC, the shafts alone were almost $2500. 6hp28 is definitely the better option.

Unless you were talking about building a 6hp28.... Either way, I just moved and it will be ~6-8 months until my shop is built :(

Honestly I was thinking similar things, because while PR may technically be "competition" I have not heard any bad things about the clutch packs themselves or how they operate/shift etc... everyone seems to be pleased and I wish them the best with that setup. The first downside to the PR clutches that I can see is the price point and overall complexity/labor involved to do the work required. Removing, rebuilding and reinstalling a transmission is a lot more labor intensive than an adapter kit and a transmission removal/install. You hit the nail on the head with the second downside of being stuck with stock shafts. While the 6HP28 shafts arent unbreakable, theyre much stronger than stock 21 shafts and I would argue/speculate (need actual testing/data) similar strength to cryo 21 shafts, maybe stronger.

In the future if we can get some billet 6HP28 shafts possibly made by a 6R80 shaft manufacturer... sky is the limit. The stock 28 shafts could also be cryo treated but I think most of us would prefer a fresh billet shaft like what the Ford Mustang 6R80 guys have used to make 2k+ TQ and legit 7 Second passes. All of that said most people on this platform just dont need 2k capable transmission yet and the market for that would be much smaller. We have some other ideas and things that may come to fruition eventually since the 6R80 and 6HP28 are so similar.

Hey any update on the XI and/or 535xi guys? My buddy has been sitting on a set of PD clutches & has a spare low mileage 6hp21/26 sitting around. its been like a year since he got it & hype/progress has died down, so I am waiting for the right moment to introduce him to this whole swap :)

He has slowed down on turning everything up, but I suspect its the 5th gear onward shift flares that is the reason why.

Hey Vonhassen, thanks for checking in! Heres an update for you and others concerning AWD.

AWD test kits and 2nd batch of RWD kits are actively being machined by me on a daily basis as of last week. We expect to ship late Oct, early Nov and already have early deposits on about half of the batch, with several others intending to pull the trigger before the end of the month. If youre friend is interested I am also offering a layaway option he can lock in the reduced cost by doing a early deposit now and make payments over the coming months until he is ready for it to be shipped. Even if he is not in the market currently we will be doing early deposit pre-sales on future batches as well in a similar fashion. AWD kits currently are in testing phase with Test pricing of $1800 shipped in USA that will never return after this initial test batch is sold.

As for progress on the actual installation and first AWD test kits...

I am actively working with one of my AWD testers to guide him through the preparation process and also help pave the way for everyone else concerning the AWD variances that everyone has to tackle. This includes E-Shift to M-Shift conversion, EGS/TCU coding, transfer case crossmember/bushings modification etc. So far everything is going well and as we progress farther I will have pictures, instructions and more details for everyone. A lot of things that have been researched, theorized and planned for months are coming together. This tester is essentially prototyping and assisting me with finalizing the AWD kits. There are also things going on behind the scene with Rod Sutphin and XHP concerning tuning, refinement, future options/different paths for controlling the transmission.

I am not one to brag but I can honestly say everyone that has installed the kit is very pleased with fitment, ease of installation, kit comprehensiveness and support provided. Everyone has been very understanding about small areas that needed improvement, the meat and potatoes of the kit have been nothing but solid and the feedback we received from testers has led to small revisions which are present in the most recent batch. We stand behind the product and will continue to ensure it is a 100% finished proper kit before we move onto another product in 2022.

Many thanks to everyone that have helped us get this far and continue to support us!
 
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nyt

Sergeant
Sep 15, 2019
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2010 335xi
I have 0 interest in working with Nizpro. I would prefer a US based manufacture that I can work directly with maybe even local to me as well for lower cost and faster availability.

Individuals are welcome to buy and do whatever they would like though.

Agreed, Nizpro was difficult.
 

135i2

Specialist
Jul 23, 2017
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76
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135i
RHD ZF6HP28 into the 135i ST.

Josh at Guru has been great to deal with through the whole process.
I did buy the wrong donor box so we have had to find a way forward with this local 530d unit.
A 330d would have created less of a headache but at least this puppy will hold a little more power and torque.

Having Advan Performance in Sydney install the Guru Kit around their other work.
Old box out, so you can see how tight the 3584RS is.

20211108_124110.jpg






The 28 with a the old 21 valve body installed.
A 335d TCU supplied by Guru is also in (the black bit).

Resized_20211112_145514.jpeg





Guru Adapter on my brand new OEM 6hp21 torque converter.
Old box in the background.

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335d TCU on the 21 valve body and in the 28.

IMG_8422.jpg





Adapter only needed minor clearance work around the ST.
Resized_20211112_145503.jpeg