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Old September 20th, 2017, 04:30 PM
bpmcgee bpmcgee is offline
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Default Re: Topping out at 55 mph?

Gerty,

Do you know what rear-end gears you have? I have 3.07s in mine, which was a factory option.

Using an RPM calculator, 3.07s:

29" tires (235/75x15s) will give you an RPM of 2490 at 70 MPH.
30" tires (295/65) it would drop the RPM to 2399 at 70 MPH
31" tire, (which some say will fit) would drop that to 2329 at 70 MPH.

Red line for the 305 is in the 3600 RPM range, so to me the answer is "Run stock 29" tires, and get a 3.07 rear end."

B

P.S. I assumed that you had a manual with a 1:1 top gear -- you didn't mention manual/auto.
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