I agree with your RPM diagnosis, but what are you going to do?
There is no other option right now to get a tall tire geared down
on the road, and the 4.24s are too low for the sand.
The Undertaker will take the Stock T-case set to an effective 2.8:1
and in my opinion, that is a better range for all around driving, low enough
for rock crawling and high enough to run sand.
If you install 4.62s you will have an effective 6.93 and with 5.12s it will be
an effective 7.69, these #s assume a final drive of 1:1, with overdrive 5th
the effective reduction will be less, but I'm too tired tonight to look up
the 5th gears OD #
So in short, an undertaker will allow you to run a 35 or even a 37-40 inch tire
and still have reduction to pull them, now if we can just figure out how to keep
the axles from twisting off like tooth picks ..............
Wild