Gear ratio with 8 speed auto

[junkyard]

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]

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]

What do you have?

 

[junkyard]

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

I'm pretty sure mine is a 3.09. Manuals have the 3.90.

 

[junkyard]

What do you have?

The current diff is 3.23 I think and is open. I want a complete third member with posi.

 

[Challenger RTA]

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]

8th gear is like 0.6667 ratio.

 

[Challenger RTA]

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.

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.

tiresize.com

Gearing Calculator | RPM and Tire Diameter to km/h - mph with Shift Tracer

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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[SFEbody]

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

 

[junkyard]

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

Cool. Thanks

 

[Woods4291]

I have 3.55 with a 28 inch tire 275/60/15. I run 2200 rpm at 75 which is perfect

 

[junkyard]

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.