Thanks for your input on the gear box. I think I'm just going to have to leave it alone for now. The truck steers too well. I installed shocks, wheels and tires 5 years ago and never had it aligned. I can let go of the wheel on the highway and the truck tracks perfectly straight. Tire wear is perfectly even across the tread. It's actually quite amazing.
There's no unusual behavior with the steering over rough roads , either so I'm virtually certain there is nop water or rust in the steering box. Eventually I may remove the gear and do all that you say but right now I don't need to do elective surgery on any of these wrecks. I have enough to do on them with actual problems.