on a 4wd, you don't want anything geared higher than 4.10 IMO. And as said before, you can't just change the rear...gotta change the front gear as well...gotta have them matched unless you wanna lose your 4x4-ability by removing your front shaft. Running different gears front to rear would cause the transfer case to bind inside. My buddy's chevy had 4.11 in the front and 3.73 in the rear and we'd wheel it....took 1/4 mile in reverse to unbind the tcase. Wasn't good on the tcase at all.
Notice how the thread jumped around a bit, Jason? Please create yourself a signature with some info about your truck. It'll help us help you alot better and faster. Year, 2wd or 4wd, engine, trans, mods, etc.
'01 XLT disguised as a '03 Fx4 Level II.