I have a '46 1/2 ton with the old style non synchro'd 4 speed. That sucker ate U-joints until about 10 years ago, when I started using about 5 oz of W140 gear lube in the small pipe fitting on top of the U-joint at the rear of the trans every 300 miles or so. I can see no evidence of the U-joint getting any lubrication from the trans. If I don't do this lubrication, the truck develops heavy vibration that is coming from the U-joint. As soon as I lube it, the vibration stops. When I go on road trips, I carry a small pump can and will hit it on the side of the road. The extra lube ends up in the transmission, somehow, and it's frequently overfull when I add the U-joint lube - I just drain off the excess. Not a great solution, but it's worked for me for over 20,000 miles and I haven't had to change out the U-joint. Would love a permanent fix, but I've heard from many folks that the U-joint is the weak point in the torque tube system and was frequently a problem.
My 2 cents,
David B.
