Looking at the calculator again something does not jive, my speed and rpm at 65 is way off. in 6th at 65 the Jeep turns about 26-2700 rpm and not 2172 as the calculator shows. As far as rubicons go they could simply shift to high range or rev them up some more. The terra lo has the rpm restriction on it never hears of that on a 231 transfer case it has a different planetary setup than the stepped gears in a terra lo. Seems to me it's more a problem of in experienced drivers to lazy or afraid to shift to high range. Also truth be told for mud wheelin a 4 to 1 transfercase is not the way to go