If you say reduction, then you are saying undedrive. The numbers are higher (ratio). Meaning in HI you have OEM setting at 1:1. Whatever goes in, goes out at the same ratio/speed.
We don't want that with bigger tires. We want a "reduction" not overdrive. The tires provide enough overdrive to drive all of us crazy here.
We want under drive for the HI gear and an even greater reduction for the LO gear.
For every revolution the tranny puts out, the transfers case in it's original state puts out 1 revolution to the shafts (both front and rear).
Lets just look at HI gear, the one you use everyday on the street.
With 33's, 35's, 37's etc you are already in overdrive. The engine spins around less (lower RPM) at a given speed. This also translates into less perceived power. Although the power stays the same, what is put on the asphalt is less. I said "perceived".
If you run bigger size tires, you want to regear the 2 differentials with a lower gear (higher numerically).
Instead of doing so, you can regear the x-case in HI and accomplish the same thing. Making the engine work harder (rev more) for each transfercase revolution.
In fact the engine goes back to it's own parameters, as it was running before with 31" tires.
A 10% reduction (higher value numerically... 1.1 gear) would the drivetrain to about 4.5:1, which is good for 33" and 35"
People with 35" prefer a more aggressive gearing of 4.88 as the tire mass increases, the inertia is a larger factor to combat, etc.
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Yep, I'm taking your word for it.
