AT Transmission options

kenhassen1 · 09-09-2022, 11:30 AM

I'm looking to get some feedback or opinions on what to do with my transmission. I have a 6hp21 that is definitely on it's way out. It was supposedly upgraded with all of the propulsive dynamics parts several years and 30k miles ago, torq conv, clutches, bushings, valve body, ect. I've been debating going to the 6hp28 or 8hp45. I considered rebuilding the 6hp21 but my experience with it hasn't been good and as far as upgrades go it seems to be a dead end. I don't think they even make the upgraded clutches anymore. Just wanted to get some ideas from everyone on this. I'm looking for a more long term solution so I'm leaning toward the 6hp28 for its durability.

iminhell1 · 09-09-2022, 12:38 PM

6hp28 you won't need a controller. 8hp you will need a controller. So that added cost should factor in. But then finding a lower mile 6hp is tough vs finding a low mile 8hp is pretty easy and should be for the future years.

My route will be 8hp. I just see it as a better option for all things performance. Internals are used by more than just bmw and it's a faster box. Pay more get more.

kenhassen1 · 09-09-2022, 04:58 PM

All good points. With the adapter plates for hp28 I think the cost is relative. I was planning on rebuilding the box before I put it in. The speed of the 8 would be a great choice and I think I would I go the cantcu route. The hp28 I believe shares guts with the 6R60 or 6R80. Both which have a lot of support in the ecoboost market but I'm not sure. My initial concern is that if a fully upgraded PD unit came apart so easily then the hp45 will certainly fail quickly as well, though I honestly believe whoever built my hp21 did a poor job.

kenhassen1 · 09-16-2022, 12:38 PM

There is an option out there for the 6hp19/21 that I overlooked.

https://www.puredrivetrainsolutions....ission-rebuild

iminhell1 · 09-18-2022, 12:26 PM

That doesn't fix the risk of the input shaft being the weakest link for sticky tires. Roll racing stuff you're at less of a risk. Dig racing, it's a time bomb.

kenhassen1 · 10-14-2022, 03:45 PM

I decided on the 6hp28 route based on that it is easier to integrate imo and has less potential quirks or software problems. Just an opinion, not hear to argue about the 8hp. As far as performance goes it can easily be upgraded to handle more power than an N54 will probably ever make. For others out there wondering, I have confirmed the 6hp28/26z shares internals with the 6R80 that is attached to most 3.5 ecoboost engines. This information is not as obviously available as you might think. I also now have 100% confirmation that the failure of my built hp21 was due to poor workmanship. I pulled the pump and drum and the snap ring that holds the clutches in fell out. No signs of wear or damage to the snap ring.

09-09-2022, 11:30 AM	#1
kenhassen1 Enlisted Member 6 Rep 32 Posts Drives: 09 135i Join Date: May 2022 Location: Colorado iTrader: (0)	AT Transmission options I'm looking to get some feedback or opinions on what to do with my transmission. I have a 6hp21 that is definitely on it's way out. It was supposedly upgraded with all of the propulsive dynamics parts several years and 30k miles ago, torq conv, clutches, bushings, valve body, ect. I've been debating going to the 6hp28 or 8hp45. I considered rebuilding the 6hp21 but my experience with it hasn't been good and as far as upgrades go it seems to be a dead end. I don't think they even make the upgraded clutches anymore. Just wanted to get some ideas from everyone on this. I'm looking for a more long term solution so I'm leaning toward the 6hp28 for its durability.
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09-09-2022, 12:38 PM	#2
iminhell1 C2H5OH 3915 Rep 2,144 Posts Drives: 2010 SG 135i auto Join Date: May 2015 Location: Darwin, MN iTrader: (1)	6hp28 you won't need a controller. 8hp you will need a controller. So that added cost should factor in. But then finding a lower mile 6hp is tough vs finding a low mile 8hp is pretty easy and should be for the future years. My route will be 8hp. I just see it as a better option for all things performance. Internals are used by more than just bmw and it's a faster box. Pay more get more.
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09-09-2022, 04:58 PM	#3
kenhassen1 Enlisted Member 6 Rep 32 Posts Drives: 09 135i Join Date: May 2022 Location: Colorado iTrader: (0)	All good points. With the adapter plates for hp28 I think the cost is relative. I was planning on rebuilding the box before I put it in. The speed of the 8 would be a great choice and I think I would I go the cantcu route. The hp28 I believe shares guts with the 6R60 or 6R80. Both which have a lot of support in the ecoboost market but I'm not sure. My initial concern is that if a fully upgraded PD unit came apart so easily then the hp45 will certainly fail quickly as well, though I honestly believe whoever built my hp21 did a poor job.
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09-16-2022, 12:38 PM	#4
kenhassen1 Enlisted Member 6 Rep 32 Posts Drives: 09 135i Join Date: May 2022 Location: Colorado iTrader: (0)	There is an option out there for the 6hp19/21 that I overlooked. https://www.puredrivetrainsolutions....ission-rebuild
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09-18-2022, 12:26 PM	#5
iminhell1 C2H5OH 3915 Rep 2,144 Posts Drives: 2010 SG 135i auto Join Date: May 2015 Location: Darwin, MN iTrader: (1)	That doesn't fix the risk of the input shaft being the weakest link for sticky tires. Roll racing stuff you're at less of a risk. Dig racing, it's a time bomb.
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10-14-2022, 03:45 PM	#6
kenhassen1 Enlisted Member 6 Rep 32 Posts Drives: 09 135i Join Date: May 2022 Location: Colorado iTrader: (0)	I decided on the 6hp28 route based on that it is easier to integrate imo and has less potential quirks or software problems. Just an opinion, not hear to argue about the 8hp. As far as performance goes it can easily be upgraded to handle more power than an N54 will probably ever make. For others out there wondering, I have confirmed the 6hp28/26z shares internals with the 6R80 that is attached to most 3.5 ecoboost engines. This information is not as obviously available as you might think. I also now have 100% confirmation that the failure of my built hp21 was due to poor workmanship. I pulled the pump and drum and the snap ring that holds the clutches in fell out. No signs of wear or damage to the snap ring.
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