[flyingtim01]

So the visual inspection turned up nothing. Nothing seems to be rubbing, no exhaust issues, no driveline issues.

Thinking over the symptoms (aggravated by bumps, worse/louder when truck is empty, much quieter when fully loaded) leads me to believe that it's one or both of the U joints. With the truck loaded to the gills and the suspension compressed, the driveline is a bit straighter, and it stands to reason that the U joint wouldn't be at such a severe angle as when the truck is empty.

Ordered up a couple Spicer 1350's and a couple U bolt kits. Funny, when you look it up on the Spicer website, they say the truck should have two 1310's. Other research I did around says that some trucks have a 1350 in the rear and a 1310 up at the transfer case. I measured mine and both are 1350's.

Hopefully get them changed out this week, and I'll report back!