*HELP* 06 Freightliner Columbia feels to be hopping

It could be a out of round tire or a tire with a bad belt that's sticking up slightly.

 

First, jack it up and check the tires for out of round. If they are out and have enough tread left, shave them to make them run true again.

Then check your driveshaft slip joints. If they are siezed, it will cause the rear ends to bind when trying to move up and down.

 

Mine was the aluminum hubs on the back warped. I don't know if they still put those hubs on freightliners. Mine was 2001. Easy way to check drums, tires , wheels hubs is to jack the drive axles off the ground and run the back so you can see the wheels turning.

 

Also the slip yoke on the shaft between the drive axles is famous for binding up on those trucks. A tell tell sign is the air bags on the rear drives will be stretched out more than the front axle bags. Easy fix is to mark where the yoke and shaft sit now. Unhook the driveline from rear yoke. Pull the shaft out of the slip yoke clean it check splines and re hook it 180 degrees from where it was.

 

Yep, you have to jack up both drives on stands and run it and watch for wheels out of round.

 

Check your ride height.