Please Help Peterbilt 388 Vibration

ok I’ve got a 388 2012 model has 400k on it. The truck has a bad vibration between 62mph-68mph ! But the vibration doesn’t just start when just get in the truck in leave you have to drive around 80-100 miles down the road and more you drive worst it gets. I’ve replaced Ujoints new drive line carriers bearings. Can someone please tell me what to do it’s driving me crazy and getting worse. And another thing I noticed when it starts if you jerk the wheel to the right the vibration gets worse!! If someone had this problem let me know what to do thanks

 

No new tires all the around had them balanced and the vibration is coming from the rear not front! Today I noticed it started right after I got up to speed usually you have to drive around 80-100 miles check all motor mounts good I don’t know what else to do could it be a power divider ?

 

Yes I’ve had 2 dealers to check ride height in specs 2 yokes has been replaced new joints as well. Had new drive line replaced the 2nd one from transmission. New u joints on the drive line between the rears also read tired are balanced too.

 

They said they were I’m gonna have them checked again in Morning it’s gotten really bad