RPMs, Axle Ratios and MPHs

7

77SSII

Member
Hey all,
I have 33" mtrs, a 727 and I think 3:73s.
My speedo is way off but on the highway around 65mph (per a hand held gps) I am spinning around 2800-2900 rpm.
Does that seem right w/you guys?

I'm gonna jack up the rear end in neutral and count tire/drive shaft revs....
 
I have 31" tires (fairly new), 3.73 gears and mine turns 2900 rpm at 65mph.

Some scouts have a speedometer corrector at the t case. Mine was way off until I took the corrector off. Now it's only about 2mph off.
 
That sounds about right. I was doing the same thing with the gps. My 74 was sporting 32" shoes and 4.56 gears and I think I was taching around 3,000rpm. Give or take some rpms, it's been almost a year now since I drove that one since I rolled it.
 
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