junkyard
Active Member
I am installing a 8HP70 in my 73 with the 392. Question is what rear ratio should I run in the rear. I want it to be plenty spirited for stop light challenges but not pegging the tack on a 60 M.P.H. cruise.
Gear ratio with 8 speed auto
- Thread starter junkyard
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scar426
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Stock for a Scat Pack Challenger is 3.90, so.......
Challenger RTA
Well-Known Member
What do you have?
junkyard
Active Member
I'm pretty sure mine is a 3.09. Manuals have the 3.90.
junkyard
Active Member
The current diff is 3.23 I think and is open. I want a complete third member with posi.
Challenger RTA
Well-Known Member
Run it see if you like the ratio,then change it.it will give you an idea.Do you know the high gear of transmission?
junkyard
Active Member
8th gear is like 0.6667 ratio.
Challenger RTA
Well-Known Member
I would say 3.90 or 3.55. Find out what 1st gear is use a speed gear and tire calculator find what you want.
tiresize.com
www.blocklayer.com
Gear Ratio Calculator
Easy to use gear ratio calculator. Use our gear ratio calculator to find the correct gear ratio to run when changing tire sizes to keep your stock gearing.
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Enter Gear Ratios, Tire Diameter and Diff Ratio to Calculate km/h mph and Shift Points with Tracer. Large Animated Gauges
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Last edited:
SFEbody
Well-Known Member
i have the 8HP70 in mine and they recommend 3.23 so i have a Suregrip with that gear set up. runs smooth
junkyard
Active Member
Cool. Thanks
junkyard
Active Member
Thank you Woods. I actually ordered a 3.55 third member a couple weeks ago. I think that will be best for me as well.
Buckminster
Well-Known Member
I'm assuming you have an 8 3/4 rearend, but if not, please elaborate. If you do have an 8 3/4 how did you handle the driveshaft?
SFEbody
Well-Known Member
I do have 8 3/4 Suregrip. I went to Driveshaft Pros, they custom made a shaft with a slip joint and the proper connections on both the 8HP70 and the rear end. I think it was about $700
Buckminster
Well-Known Member
Thank you! I have been scouring the forum looking for driveshaft solutions and i've had trouble finding much discussion on the topic.
SFEbody
Well-Known Member
They are a franchise in California only I think. I can ask some friends in St Charles County if you need some sources. I used to live there. DriveshaftPro // Driveshaft Repair in Southern California
Buckminster
Well-Known Member
I'm sure there are driveshaft places in St. Louis, just haven't looked yet. If you do know someone, that would be very helpful and much appreciated. Happy New Year!
In a manual, not an auto
That has to be the best website I have ever seen! Thanks for that. They will get my business for sure.
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