Stock gears, large tires, and the transmission

Its common knowledge that you suffer a power loss retaining stock gears and putting on larger tires (31's, 33's or whatever). Most of us using such a combination typically run in 3rd to keep our RPM's up. What I wonder is: in a situation where you are say, loaded down with gear and/or going up a long grade, is the well being of the transmission compromised when running less than ideal gearing even though you make sure to go slow enough to keep the RPM's in the 2300 to 2800 range? If so, what am I not accounting for?

You aren't accounting for the stress you get from accelerating off of the line, but once you're on the highway running in '3' is fine.

Make sure you put a big trans cooler on, even with proper gears.

I'd say that heat is a tranny's worst enemy, next in line being too much strain on the output shaft.

if you are rockcrawling I'd say you're at risk of overloading the tranny in both ways.


If you run a tranny cooler and are running at speed in the correct rpm range, all you'd have to do is go easy starting at stoplights and the tranny wouldn't know the difference.

you'll likely blow through tranny fluid faster, though, with increased temps and load. I'd shorten the service intervals for the tranny, as a preventative measure.

With stock gears and 33s, you're making the engine/transmission work harder. It's like driving an underpowered stick shift, you've got to slip the clutch a little to get going uphill, off-road, carrying a load, etc. That's bad for the clutch. The torque converter replaces the clutch in the autos, so the torque converter has to slip a little more than normal to get the engine in its power band. That causes extra heat in the the tranny, which makes your fluid burn up faster. I second Cal on the tranny cooler.

Running in the 3 position is better because it locks the torque convertor as opposed to the tranny downshifting automatically and not locking the torque convertor. When the TQ slips it generates more heat, which is bad for the tranny. Def get an aux cooler and bypass the cooler in the radiator to help the engine run cooler as well.