Quote:
Originally Posted by albertan82
Hi ,
I have a 1964 C10 Stepside - short wheelbase, with 350 5.7 vortec and TH350. Tires are 225/75R15 (28.5").
Current differential is from a 1973 Chevrolet Caprice (350 engine) added to the truck by the previous owner, but I do not know the current gear ratio. It is the 10 bolt, 8.5", 28 spline differential.
When I drive on the highway at 60mph, tach is showing around 4000rpm  (
What gear ratio would be the best for this engine-trans-tire combo?
Thank you all in advance 
From:
Istanbul, Turkey |
I'd get another tach and see if that one is reading correctly..
at 4000 rpm with a 28" tall tire, and a 1 to 1 3rd gear (th350) at 60 mph
is a rear gear of 5.56 not likely..
you can get a ballpark,, by putting the rear axle of the car on jack stands..
mark the driveshaft. and mark the tire put the car in neutral , car not running..
and turn the driveshaft until the tire makes one full turn/rotation.
counting the # of times the drive shaft turned..
it turns 3 and 3/4 times.. most likely have 3.73 gears
3 and 1/5th 3.23
just over 3 3.07
3 and just under a 1/2 3.42
little over 4 times. 4.11
etc.