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2018 R/T AWD Black Blacktop AUXIT LED directionals, Window tint, Whipple Supercharger stage 2
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Discussion Starter #1
Hello all,
I have a modified 2018 RT and want to remove the 117 mph governor. The new tow-n-go has a new limit of 146. I have confirmed both vehicles have the 8HP70 transmission but I am trying to understand what other differences allow the new one to go past the 117. I was told that drive shaft may be the culprit but want to be sure. Has anyone done a deep dive on the 2021 yet? If it as easy to replacing the driveshaft and a re-tune I would be very happy but modifications are usually never that easy.

any insight?
 

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Hello all,
I have a modified 2018 RT and want to remove the 117 mph governor. The new tow-n-go has a new limit of 146. I have confirmed both vehicles have the 8HP70 transmission but I am trying to understand what other differences allow the new one to go past the 117. I was told that drive shaft may be the culprit but want to be sure. Has anyone done a deep dive on the 2021 yet? If it as easy to replacing the driveshaft and a re-tune I would be very happy but modifications are usually never that easy.

any insight?
It’s all about the calibration (parameters) set in the PCM from the factory. I have a 2016 R/T and I can go that fast (and even a little more) !


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Your factory tires would be T speed rated. That rating is only good for 118 MPH. That is why it is governed at 117. The tow and go gets the SRT wheels and tire options with a higher speed rating. As awehlage said a tune can change the limiter, but be aware of the speed ratings of the tire you are running.
 
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2018 R/T AWD Black Blacktop AUXIT LED directionals, Window tint, Whipple Supercharger stage 2
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Discussion Starter #4
Your factory tires would be T speed rated. That rating is only good for 118 MPH. That is why it is governed at 117. The tow and go gets the SRT wheels and tire options with a higher speed rating. As awehlage said a tune can change the limiter, but be aware of the speed ratings of the tire you are running.
I was told by whipple that the issue is with the driveshaft. Tires are an easy fix.
 

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I was told by whipple that the issue is with the driveshaft. Tires are an easy fix.
LOL!
I could see it breaking on launching with the additional Whipple power so maybe that's what they are talking about...but no way an increase from top end from 117 mph to 150 mph is causing any more stress to failure.
The SRT and 5.7L use the same rear driveshaft...doesn't the SRT run 160+ top end?
 

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Discussion Starter #8
LOL!
I could see it breaking on launching with the additional Whipple power so maybe that's what they are talking about...but no way an increase from top end from 117 mph to 150 mph is causing any more stress to failure.
The SRT and 5.7L use the same rear driveshaft...doesn't the SRT run 160+ top end?
Not because of launch. The tune I got from whipple still had the governor on. When I asked why, they said there have been reports of driveshaft issues. SRT has a different driveshaft. Quick search on Rockauto shows different part numbers, widths and weight
 

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Not because of launch. The tune I got from whipple still had the governor on. When I asked why, they said there have been reports of driveshaft issues. SRT has a different driveshaft. Quick search on Rockauto shows different part numbers, widths and weight
Correct, that’s what I found as well.


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Just the front looks to be different...from what I researched it looks like the rear driveshaft is the same between the 5.7 and 6.4 SRT.
So it could be the front driveshaft has the issue. I'd pull it have it balanced checked at a driveshop and go.
 

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Just the front looks to be different...from what I researched it looks like the rear driveshaft is the same between the 5.7 and 6.4 SRT.
So it could be the front driveshaft has the issue. I'd pull it have it balanced checked at a driveshop and go.
So I talked to my Dodge parts guy at my local dealership.
He checked and noted they are different P/N's so you are correct.
5.7L P/N 52123635AB
6.4L P/N 53010845AB
Now it gets a bit interesting as he said you can bolt the 6.4L driveshaft in place of the 5.7L one as they have the same coupling due to they both have 230mm rear diffs. and transmissions. He has been right in the past as he is a Mopar guy who races an old Mopar...but I can't confirm that.
Both are 2 piece driveshafts so a 1 piece should be stronger.
 

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Discussion Starter #13
So I talked to my Dodge parts guy at my local dealership.
He checked and noted they are different P/N's so you are correct.
5.7L P/N 52123635AB
6.4L P/N 53010845AB
Now it gets a bit interesting as he said you can bolt the 6.4L driveshaft in place of the 5.7L one as they have the same coupling due to they both have 230mm rear diffs. and transmissions. He has been right in the past as he is a Mopar guy who races an old Mopar...but I can't confirm that.
Both are 2 piece driveshafts so a 1 piece should be stronger.
That is good news and answers another question I had. A Mopar tuning shop in GA told me that the SRT has a different transmission, the 8HP90. I know the trackhawk and new hellcat version have an 8HP95 with a beefed up transfer case but was unclear of all the connection points and how deep the similarities are. Thank you!
 

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Discussion Starter #14
Whipple is most likely playing the lawyer card so they don't get sued when someone wrecks at 180 mph.
Possibly. I know going that fast isn’t going to happen safely in a 5300lb Durango until I do some serious upgrades on the brakes.
 

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That is good news and answers another question I had. A Mopar tuning shop in GA told me that the SRT has a different transmission, the 8HP90. I know the trackhawk and new hellcat version have an 8HP95 with a beefed up transfer case but was unclear of all the connection points and how deep the similarities are. Thank you!
Shows 8HP70 right on the SRt window sticker

118912C8-E17A-443C-944E-857F819E9BA1.png
 
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