Hey guys, I've got an 83 jimmy, 6.2, and i live in northern california... lots of mountain highway driving. But even on level highways my overdrive can't maintain 65 without jumping from 3rd to 4th constantly. Not to mention by the time i hit the hills... 3rd gear just loses spead all the way up. It's sad when i'm following big rigs trying to catch a draft going up the hills. Would new diff. gears help this? I'm just running 33 inch mud terrains right now with stock ride height.