[QUOTE]Originally posted by Grigg:
[QB] This will help figure speeds.
http://www.drivetraindirect.com/t_gear_calculator.htm I don't know for sure what speeds a 5.9 likes to be run, but your numbers sound high to me. While I do believe it will turn that fast, you will burn lots of fuel, and shorten the life.
For best fuel economy you want the rpm at your preferred speed, say 68 mph, to be the same as, or 100 to 200 rpm over the speed that the engine makes it's peak torque. I am thinking 1800 is about right for the 5.9, but do some checking to be sure.
with 4.88 gear's 33" and .60:1 over ( unheard of steepest OD i've seen is .62:1 ) 68mph@2027rpm. . . not possable to get this rev's below 2200rpm. . .
4.88 gear's 33" tires 245/70R19.5/8R19.5 = 32.8"-33.2", Biasply 8-19.5 33.8"-34.6" my bias mudder's bald measure 33.25" my 3 good used measure 33.75"<<< 2 used General super all grip8ply in 19.5's,1 used firestone super traction 8 ply.
when i bought new set of the 8-19.5 firestone super all traction 8-19.5LT 10ply biasply mudders in 1998 i measured them at 34-3/8" tall. . .
5spd: .73:1 2466rpm@68mph. with 33" in tires.
6spd: .76:1 2568rpm@68mph. with 33" in tires.
.60:1 = 2027rpm@68mph. . .
truck is going to be a rever, Ford run's the power stroke with the 4.88's and 32" tire's. . .
Mike
