THANK YOU! Best answer yet. Was wondering what these came with originally. In your opinion would I be better off going back to a 445 or replace front with 410?. Any risk to my I5? It feels underpowered now..

 

You are missing the point.

Both the Front and Rear Differential gear ratios should be identical ALWAYS as the H3 is a FULL TIME AWD, you are destroying your T case every time you move, doesn't matter which T Case position you are in. Change the rear back to 4.56 and do it before you drive it any further.

Taint had an early AM typo, all the I5s have 4.56:1.

 

Regardless, first you need to match the axles! The starting point is to understand what the drive-axle ratio means and how it affects truck performance. The drive-axle ratio represents the relationship between driveshaft revolutions (driven by the transmission/transfer case) and drive-axle revolutions. Usually a whole number and decimal fraction, the drive-axle ratio is a comparison of the number of gear teeth on the ring gear of the axle and the pinion gear on the driveshaft. For example, a 4.11:1 ratio means there are 4.11 teeth on the axle's ring gear for each tooth on the driveshaft's pinion gear. Or, put another way, the driveshaft must turn 4.11 times to turn the wheels one full revolution. What does this ratio mean in practical, performance terms? Here's the typical rule of thumb: The higher the numerical ratio, the slower the gear will be. This higher ratio gives a truck greater pulling power, but since the engine must work harder to spin the driveshafts more times for each turn of the wheels, top-end speed and fuel economy are sacrificed. The inverse also holds true. When numerical ratio is lowered, available top-end speed is increased. Since the engine doesn't have to work as hard to turn the wheels faster, fuel economy improves. The downside is that pulling power diminishes.

 

no doubt you know your stuff but the way this is written it is confusing with contradictory comments. read it again slowly!

im guessing that a sweet spot is designed in at a band of speed to get best mpg and performance. raise or lower the ratio and you start to loose.
we know that bigger tires,(lower ratio) reduces mileage. same as gears. this does not mean that smaller tires will keep increasing mpg as size goes down, (or gear ratio goes up)
no free lunch.