Can rust jacking in-between double frame rails cause driveline issues?

Ride height comes to mind as well as what suspension. Does it lean in the front one way or another? U- bolts loose on the rear can make it hell to get ride height set. Broke tie bolts and on the rear can wreak havoc. Course everyone says you don’t need a rear transmission support anymore but with a 15, 13 or 18 I seem to think the old spring loaded bolts Pete used for years sure help.

 

For some reason Peterbilt is big on putting an insert where the rear suspension is bolted to. I'd suspect that is what OP is refering to and not a full double frame.

 

Phasing?

 

Just curious where you got 3 clutch brakes from….??

 

JD

 

No clue how I missed that part, I’m going back to sleep….

 

As oldschooler suggested I would also be checking the slip joints. Honestly from everything else you mentioned I don’t know what else could be the problem. If you drive shaft is that badly out of balance to trash things that quickly it would almost have to be visibly bent.