1999 peterbilt 379 ext hood bounce wobble

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 feel very little 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 do have an unexplained buckling of my steer tires. It looks like a saw blade effect. Bridgestone 283
i have spun the tires to check for out of round, wobbling etc no such luck there.
Please any advise would be greatly appreciated.

 

The treads are turned up. The inside of the tread is turned up all the way around the tire.
Yes vibration was there before all of this work.

 

Thank you! I'm concerned it maybe a rear end because the back rear end does have some slack in it. Last night I did notice that when I was in a pull and let off the throttle going up a hill the truck ran smoothly but once I accelerated that is when the truck started bouncing again. Could it possibly be a rear end issue or transmission issue. I also do need a 3 axle alignment but I hate to keep sinking money in stuff that wasn't broke to begin with.

 

Just had to replace the front rear end today with the power divider. Metal chunks of stuff was in the housing of the rear end. I'm hoping this will solve my problem