So I got a call from the shop today and the gentleman informed me that indeed the slip yoke is bad, there is no way the drive line is causing the knocking/ banging I have. So he told me to start looking into the T-case/ transmission for bad bearings. At this point I should let you guys know what my exact problem is since you guys are very knowledgeable. 1st gear there is no noise regardless of how hard I get on it or coast, second gear towards the end it starts knocking about 20 mph, 3rd gear sounds like the truck is ready to grenade itself. The knocking is so loud and violent it sounds like someone with a framing hammer beating the crap out of the floor board beneath my feet, and a jack hammer under my seat worth of shaking. If I am accelerating or coasting it does not really change much. If I step on the clutch it goes away and coasts smooth in any gear at any speed. If I let the clutch out say to slow down it comes right back. Up hill, down hill, with my 10k trailer loaded there is no difference its the same. It always goes away if I step on the clutch.
So I pulled out the front drive line and drove it with no change. I put the front drive line back in and pulled the rear one out, I then drive the truck in 4-high and the sound is gone. This is why I thought it was the drive line. I know harmonics can do crazy things but I swear it's coming from under my feet or close to it. I am going to pull the rear diff cover tonight for a look see.