Wife'e jeep is an '06 LJ, 4.0, 6 speed manual, OEM tire size, 2" lift.
Living in Denver, even the slight inclines we have around town and in the foothills are enough to cause the Jeep to loose speed in 6th running 65+ mph. Pretty much runs in 5th all the time and occasionally has to downshift to 4th on some hills (have not taken a trip into the mountains yet, so I know that holding the speed limit is not gonna happen).
I have no clue what axles are under it. I know the front diff cover is round/circular, can't remember if the back is the oddball shaped cover.
Anyhow, running 65mph in 5th holds the engine around 3k rpm. I am guessing the axles are probably 3.73.
Eventually the wife will be towing a 2k# pop-up camper behind it. Once that happens, I know she is going to loose even more holding power, even on the flats.
Aside from installing an under-drive unit (not even sure it would fit, but would be cool to have a 12 speed). Most of the outer city highway speeds are 75mph. Having the engine purring along at 3200 - 3700 in 6th at that speed would be fine.
What gear ratio should we be looking at?
What should I expect to pay to have it done?
What kind of impact are we going to see fuel economy wise (running unloaded)?