[my98tj]

if you're getting them for free, then just try it and see how bad it is. i have the same transmission and one of these years when i get to 35's, i'll be going with 4.56 gears.

 

[idiot magnet]

You'll be much happier with 4.88's with 35's and an auto. Consider 5.13's if you have D44's and if you don't get a HP30 and build that until you are ready for the 35's.

 

[Ironhead Jed]

You'll be much happier with 4.88's with 35's and an auto. Consider 5.13's if you have D44's and if you don't get a HP30 and build that until you are ready for the 35's.

he has the 3 sp, not the 4 sp. 4.88 or 5.13 would be overkill for 35's with that trans

 

[jsuggs]

There is a mathematical formula for this. It calculates the number of inches your vehicle moves forward with each turn of the driveshaft. Then you can figure what gear ratio gets you the closest to that for what tire size you want to use. Just make the appropriate substitutions in the formula.

tire height in inches x 3.14 / gear ratio = roll out

The closer that you stay to the stock number the more stock the jeep will run, the more accurate the speedometer will be, etc.

Jeremy
ASE Master Auto Tech

 

[my98tj]

i always look at it like it's a ratio of gearing to tire height and you want the new ratio to equal your factory ratio.

factory gearing: 3.73
factory tire height: 30
new tire height: 35
new gear ratio: unknown (x in the equation)

3.73/30=x/35
solving for x gives you a ratio of 4.35 which doesn't exist, so you can either stay with the 4.10s or go up to 4.56s.

 

[Jerry Bransford]

With the OP's 3-speed 32RH transmission, 4.56 is ideal for 35" tires. 4.10 would work, an automatic transmission is more forgiving of an improper axle ratio, but the engine RPMs would be a little lower than would be optimal.