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Gear ratio with 8 speed auto

junkyard

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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.
 

scar426

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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.
Stock for a Scat Pack Challenger is 3.90, so.......
 

Challenger RTA

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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?
 

Challenger RTA

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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.
 
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SFEbody

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i have the 8HP70 in mine and they recommend 3.23 so i have a Suregrip with that gear set up. runs smooth
 

Buckminster

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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.
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

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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

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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
Thank you! I have been scouring the forum looking for driveshaft solutions and i've had trouble finding much discussion on the topic.
 

Buckminster

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