Deeper gearing will also help prolong the life of the transmission, for three major reasons:
- The torque converter will lock up sooner and at lower speeds, and will remain locked for longer. When the torque converter is unlocked, a significant amount of mechanical energy is wasted as heat. (Hence why fuel economy is better with a locking torque converter.) Generally speaking, the hotter a transmission runs, the shorter its life will be.
- The additional rotational speed of the transmission will increase fluid flow through the transmission cooler, helping to reduce the temperature of the transmission, and also helping to heat it in cold weather.
- Less slip will be required from the torque converter during acceleration from a standstill. This is due to the gearing reducing the overall torque demands on the transmission. The overall reduced torque demands can also extend the life of the clutch packs in the transmission.
This all the way.
My first Rubicon was on 35’s and after I finally regeared to 5.13’s, the tranny temps went down approximately 20 degrees across all conditions and fuel economy went up, in fact, the best fuel mileage I ever got with that Jeep was with 5.13’s and 35’s, even better than when it was completely stock.