8HP70 to 8HP90 swap - Useful info for the next guy.

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Josh22855

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I recently swapped my 8HP70 out for a 8HP90 on a 2016 Ram 1500 single cab, the HP90 trans was from a 2016 Hellcat (Thanks ebay!).
The bottom 2 bolts on the transmission bracket I moved back 1 and 1/8th inch and the 4 vertical bolt holes will have to be drilled out in order to bolt to the end of the transmission. I was not able to get the passenger bottom side bolt in because the bottom bolt on the horizontal bracket was in the way.
You cannot use your torque converter from the 8HP70 transmission, the 90 input shaft is larger. The Flex plate does not have to be replaced.
You may also want to explore other bolt options for the output yoke on the driveshaft, there is absolutely no room for a socket to fit on 2 of the bolts.
You can see each part # in turquoise in these photos, I did not get a photo of the dust cover, you will have to drill out a hole for the starter. The factory dust cover AND factory starter will not work on the swap.
Hope this info helps out the next guy.
 

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Wild one

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I recently swapped my 8HP70 out for a 8HP90 on a 2016 Ram 1500 single cab, the HP90 trans was from a 2016 Hellcat (Thanks ebay!).
The bottom 2 bolts on the transmission bracket I moved back 1 and 1/8th inch and the 4 vertical bolt holes will have to be drilled out in order to bolt to the end of the transmission. I was not able to get the passenger bottom side bolt in because the bottom bolt on the horizontal bracket was in the way.
You cannot use your torque converter from the 8HP70 transmission, the 90 input shaft is larger. The Flex plate does not have to be replaced.
You may also want to explore other bolt options for the output yoke on the driveshaft, there is absolutely no room for a socket to fit on 2 of the bolts.
You can see each part # in turquoise in these photos, I did not get a photo of the dust cover, you will have to drill out a hole for the starter. The factory dust cover AND factory starter will not work on the swap.
Hope this info helps out the next guy.
Good info Josh.
 

savage_46

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I believe I remember reading on wiki that the 8hp trans are only offered in 2 case designs (rwd & 4wd). At least during the DS/WK/LC/LA lifespan, may change with new chassis designs like WL. My theory is that a 8hp90 from a trackhawk or hellcat durango should be a direct bolt in cause those are 4wd/awd. Somebody who has seen multiple of the 8hp90 may be able to confirm.
 

Wild one

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I believe I remember reading on wiki that the 8hp trans are only offered in 2 case designs (rwd & 4wd). At least during the DS/WK/LC/LA lifespan, may change with new chassis designs like WL. My theory is that a 8hp90 from a trackhawk or hellcat durango should be a direct bolt in cause those are 4wd/awd. Somebody who has seen multiple of the 8hp90 may be able to confirm.
The Trackhawks /Durango's / TRX's use the 8HP95,which is rated at 701 lb-ft,the HP90 is rated at 663lb-ft.
 

savage_46

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The Trackhawks /Durango's / TRX's use the 8HP95,which is rated at 701 lb-ft,the HP90 is rated at 663lb-ft.
Those ratings would work for the majority of us here. Do the srt/hellcat valve bodies work in the trucks & not throw config codes? Is the valve body required for launch control when adding srt pages?
 

Wild one

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Those ratings would work for the majority of us here. Do the srt/hellcat valve bodies work in the trucks & not throw config codes? Is the valve body required for launch control when adding srt pages?
You'd have to talk to somebody like Jon Sipple of Sipple Speed, Charles Barrett of Hellraisor or Russell at Sound German for that info,i haven't dug into the swap enough to answer those questions.
 

HEMI-FI

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I recently swapped my 8HP70 out for a 8HP90 on a 2016 Ram 1500 single cab, the HP90 trans was from a 2016 Hellcat (Thanks ebay!).
The bottom 2 bolts on the transmission bracket I moved back 1 and 1/8th inch and the 4 vertical bolt holes will have to be drilled out in order to bolt to the end of the transmission. I was not able to get the passenger bottom side bolt in because the bottom bolt on the horizontal bracket was in the way.
You cannot use your torque converter from the 8HP70 transmission, the 90 input shaft is larger. The Flex plate does not have to be replaced.
You may also want to explore other bolt options for the output yoke on the driveshaft, there is absolutely no room for a socket to fit on 2 of the bolts.
You can see each part # in turquoise in these photos, I did not get a photo of the dust cover, you will have to drill out a hole for the starter. The factory dust cover AND factory starter will not work on the swap.
Hope this info helps out the next guy.
Good Stuff Josh, doing lots of research now.
 

Wild one

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Thanks! I just did my first WOT data log for Z (tuner). It shifts amazing compared to the hp70
The 90 has always had a better shifting rep then the 70 has. I wished they'd stuck the 90 into the naturally aspirated 6.4 cars,as that's the one thing i dislike about the wifes 1320,is the crappy full throttle shifts.It's a bit better now that the car and tranny are tuned,but it's still not as good as a stock Hellcat shifts.
 

Dusty

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I recently swapped my 8HP70 out for a 8HP90 on a 2016 Ram 1500 single cab, the HP90 trans was from a 2016 Hellcat (Thanks ebay!).
The bottom 2 bolts on the transmission bracket I moved back 1 and 1/8th inch and the 4 vertical bolt holes will have to be drilled out in order to bolt to the end of the transmission. I was not able to get the passenger bottom side bolt in because the bottom bolt on the horizontal bracket was in the way.
You cannot use your torque converter from the 8HP70 transmission, the 90 input shaft is larger. The Flex plate does not have to be replaced.
You may also want to explore other bolt options for the output yoke on the driveshaft, there is absolutely no room for a socket to fit on 2 of the bolts.
You can see each part # in turquoise in these photos, I did not get a photo of the dust cover, you will have to drill out a hole for the starter. The factory dust cover AND factory starter will not work on the swap.
Hope this info helps out the next guy.
Which PCM and TCM did you use? Any harness/wiring issues?

Regards,
Dusty
2019 Ram 1500 Billet Silver Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 3 June 2018. Now at 69453 miles
 
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Josh22855

Josh22855

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Which PCM and TCM did you use? Any harness/wiring issues?

Regards,
Dusty
2019 Ram 1500 Billet Silver Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 3 June 2018. Now at 69453 miles
Factory PCM, unlocked, and I used the TCM that was in the 8hp90. LUCKILY the tcm and pcm were from 2016 and in that year the pcm/tcm mismatch can communicate with each other without problems, although my tuner still had to send me a trans tune. Initially I only had reverse and 1 gear in drive until the tune was sent to me.The TCM plug Is a direct fitment, nothing had to be modified.
 

HEMI-FI

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I spoke with Curt Dusterhoff in regards with the HP90 swap and he said they wouldn't have an issue tuning it.
 

Zunigajr

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Factory PCM, unlocked, and I used the TCM that was in the 8hp90. LUCKILY the tcm and pcm were from 2016 and in that year the pcm/tcm mismatch can communicate with each other without problems, although my tuner still had to send me a trans tune. Initially I only had reverse and 1 gear in drive until the tune was sent to me.The TCM plug Is a direct fitment, nothing had to be modified.
I currently did a v6 to v8 swap so going the transmission went from 8hp45 to 8hp 70. When I start it I have messages on the dash and only have revers and first gear as well. Who did you have to tune that to get it to drive properly. The engine turns on and idles perfectly just the transmission issues I’m having now
 
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Josh22855

Josh22855

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I believe this guy will be able to help you with that.
 

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malibudave

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I currently did a v6 to v8 swap so going the transmission went from 8hp45 to 8hp 70. When I start it I have messages on the dash and only have revers and first gear as well. Who did you have to tune that to get it to drive properly. The engine turns on and idles perfectly just the transmission issues I’m having now
I am not sure of the year of your vehicle, but from my research on doing a v6 to hemi swap in a 2018 JGC is that the TCM has a VIN and it needs to be recognized by the other modules for the car to operate properly.
From my research, it looks as if the 845re and 8hp70 valve bodies and TCMs can interchange. If someone has evidence that they cannot, please verify.
In my mind, your choices are:
A: Put the 845RE Valve Body and TCM assembly in the 8hp70
B: Put the 845RE TCM on the 8HP70 Valve Body
C: Have the 8HP70 TCM programed with your vehicles VIN

From my research, the stock unlocked 3.6 ECM will allow a hemi tune.

Bottom line is, all body modules have to have the same VIN number programmed into them.
The ECM needs to have your cars VIN programmed into it and the 8HP70 TCM needs to have your cars VIN programmed into it.

That being said, this is all speculation as I have not pulled the trigger on the swap yet.

I am researching "programming" side as I want it to start and run after I install everything.

Please post with any solution that you come up with.
 
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