Freightliner Columbia shaking above 60

Ive been chasing an issue with my columbia for 4 years now, its driving me nuts. The truck has a tire frequency harmonic shake above 60 mph, worst around 67. Its perfectly smooth for a max of around 10-30 seconds then starts shaking the back of the sleeper rattling the cabinets, and progresses from there like a wave through the floor, then into the seat, then into the steering wheel and the dash. Then it stops completely for another 10-30 seconds before it repeats the cycle. Letting it off the throttle vs full power makes no difference, coasting down vs pulling a hill makes no difference. The only thing that changes is its much less noticeable when loaded with 45k in the box. But with light loads or empty its a pain.

200k miles ago I replaced the following with no change to the issue:
1. Kingpins
2. Front brakes
3. Front wheel bearings
4. All 3 Driveshafts plus balanced with new carrier bearing and new u joints
5. All shocks
6. Cab mounts
7. Engine mounts
8. Rebuilt trans and both rear ends
9. New air bags
10. Leaf spring bushings
11. 3 axle Alignment
12. New brake drums and shoes
13. Leveling valve and adjusted ride height
14. Torque rods i think you call them?
15. Put balance beads in tires
16. New clutch

This past month I did some more work and replaced:
12. All 10 tires with new bridgestones
13. All Steel inners and checked aluminum outers for out of round, no issue found
14. 1 bad scam with worn bushing plus shoes and drum
15. All 4 drive axle hubs and bearings
16. Messed with Ride height about a milion times with no change, set it to stock, low, and high with no change, its back to factory height.
17. Ditched the bead bags and installed cemtramatics on all 3 truck axles.
18. New trailer hubs, bearings and tires (recaps)

None of that made any difference at all, during that process I found 3 out of 4 bent drive axle shafts. All 4 were replaced. This took out 50% of the shake to where its barely noticeable when loaded at max gross only, and more intermittent as explained above. Before this it would shake loaded or empty all the time.

This is taking all the joy out of trucking, please help!

 

Yes, they are all in phase and the driveshaft is balanced. Its an 04

 

Wow thats crazy, ill definitely keep an eye on the steering gearbox but I dont think its the issue as 90% of the shake is in the seats and the floor. Also it shakes when its on stands so that pretty much rules out the front