I seriously question its worth. Most RV's are geared to tall theses
days anyway and do not need to be geared taller. A underdrive unit
would be far more feasible/usable and all the listing I see are for OD
units. A serious tow vehicle needs the option of deeper gearing not
taller. These OD unit will do nothing to boost startout and low speed
pulling power which some seem to forget. Now if you would regear truck
with depper axle ratios and than ad a OD splitter you would have
something but as it stands I see little value in them and they do
nothing to reduce tranny strain as they put the tranny output into a
taller ratio and add strain, not reduce it.

http://classictrucks.com/tech/0509cl_gear_16/

What do you think of this performance mod?  Anybody done it?

The GEAR VENDORS will give you Gear-Splitting to fix those wide ratios with
a gear between each of them when you want it for tremendous gains in
performance (see Final Drive Ratios). Whether you are accelerating with a
Supercharged sport truck or climbing a hill with a heavy load in tow behind
your diesel - gear-splitting = performance.

http://www.gearvendors.com/f2wd4s.html

Agave
Salud, dinero, amor y tiempo para disfrutarlos
01 F350 PSD Crew Dually