Here's my thoughts. I have a 54 2-ton with 235 and it has the insert bearings. It likes to run best, quieter, and less vibes at 45. I can run it at 55 easily for clip down highway to work. I have had it up to 65 max and it's screaming by then. It takes awhile to go from 60 to 65 too. Now most big trucks are low geared, but it seems about right for other AD's I've had in p/up size. Even the 60's trucks with 250's in them and Basic models didn't go too fast w/out screaming!
