The same would be true of "slop" in the transmission, right? I've even seen engine vibrations give a "road humm" before.
Denny - do you use a hand pump grease gun? If so - stop in J-Lube next time you are out in the truck, and get a "lube only." A lot of times their pneumatic grease guns may be able to push the grease into places where hand pumps can't. Be sure they catch all the fittings.(Isn't it around 20?) It's odd that the oscillation disappears when the load is off of the truck, then comes back on the road.
