1999 379 ext hood bounce

I have a 1999 379 peterbilt ext hood with a terrible bounce wobble. The bounce/wobble is about to beat me to death and it does it around 60-65mph really bad. If I am fully loaded weighting 80000lbs I still feel the bounce or wobble. I am pulling a brand new Fontaine infinity flat bed. As soon as you take weight off of my trailer the truck begins to bounce wobble beat me to death. It is literally about to drive me crazy.
I have replaced the 5th wheel plate,cab bushing, stabilizing bar on back of cab, cab shocks, all shocks on truck including steers. I have brand new brake drums and brakes. (Brake drums are Fleetpride brand) New tie rod ends. I have had my tires balanced all tires balanced. I have rotated the tires. The truck is still beating me to death.
I have checked to see if there are any tires out of round. I feel the shake mostly in the floor of the truck. I have recently replaced the clutch. New flywheel. New bearings in the power divider. New bearings in the front nose cone of the rear chunk.
I did have unexplained buckling of my steer tires. It looks like a saw blade effect. Bridgestone 283
i recently replaced the two tires with brand new tires and also had an alignment . Also I've just put a brand new power divider in and a brand new transmission
i have spun the tires to check for out of round, wobbling etc no such luck there.
Please any advise would be greatly appreciated.
I'm leaning toward a warped drive shaft. All of my drive tires are showing the exact same wear so if it's a broken belt or something they would be showing wear. Several of my buddies have rode beside the truck going down the road and they haven't seen anything either weird with the tires I've had the truck jacked up running at the shop put the leveling valve in every position possible. Any ideas would be greatly appreciated!!

 

I think it may the back rear end. Took small drive shaft out and turned it quarter of a turn before it caught you can hear clanging in the rear end when turning it by hand. I do not hear anything when running the truck bc I have straight pipes on the truck sure hope this fixes my problem once I get that rear end in.

 

Replaced back rear end and new axles still having the same bounce rear end needed replacing the oil was gooby ( I just recently had new oil put in it) and full of metal shavings. It's gotta be a tire or rim. Just gonna drive it so tired of messing with it and the tires are to new to buy more.