Well I never understood that whole 500 mile garbage myself. They say it is to brake in the gears in the diffs and would think that is the same reason the manual gets the same requirement.
My question is this, are MD and higher trucks gears built differently? If not why do they not have the same "run in" requirement as to the brake in? I can tell you no trucking company is going to drive their trucks around empty for 500 miles! Not going to happen. UPS truck are shipped to the terminal they will run out of and some minor work is preformed at their shop then they are sent out on the road without any brake. I watched happen at the Toledo terminal, 50 brand new Macks were delivered during the Christmas season when I was working as a seasonal driver in 07. You can trust me when I say they get drove hard right out of the box!
Don