Griff in Fairbanks wrote:
StingrayL82 wrote:
I use this site and plug in the numbers
(1:1 on the transfer case, since it's a 4WD site): Final Drive RPM Calculator
2587 RPM @ 55MPH
2822 RPM @ 60MPH
Something's wrong 'cause I'm getting slightly different figures ... working them out myself.
Maybe you used LT235/75R16 instead of LT235/85R16. (Larger tire diameter and circumference means lower RPMs.)
Will post my figures in a few minutes ...
My tires are 225/75-16 (29.29" tire diameter), which is the closest thing I could get to the original 8.00-16.5 tires. Funny thing is that, per the service manual, my rig should have had a 39-tooth speedo gear, but when I had it rebuilt, we found a 38-tooth. Having done the math, the 38-tooth gear will work very well with the new tires, to within 1/2MPH.
