379 bouncing bad

I've heard of this problem from a Pete alignment tech. The cure is an adjustment to the rear suspension components although I cannot recall exactly what they do. You might talk to a good Pete alignment tech that would be familiar with the procedure. There were factory campaigns on this issue so any Pete dealer should be familiar.

 

You could call Mid America Peterbilt and talk to the service dept. They'll tell you exactly what needs to be done.

 

As I recall, it's a pretty big job involving removing rear suspension parts and flipping them then alignment of the drive axles. He briefly described the procedure to me but I was preoccupied at the time and it's been a while. The issues you describe are exactly the same issues he was describing on low air leaf susp.

 

I would check the sway bar end bushings on that little short bar in the center right at the rear of the cab or sleeper depending on whether it is a day cab or not. Its in between the two cab air bags. If those bushings are out in either end it lets the cab reel aroud in the back and cause a thumping or knocking noise even if the mounts or cab airbags have been changed i would check that also you can usually pusharound on the rear of the cab or sleeper and here it bumping around and making noise. It don't really sound like its in the suspension if you can feel it while your being loaded at a dock while stoped.

 

could the leveler be bad?

 

yeah it could be but im still a little unclear of his bounce. I can see it bouncing aroud over bumps but not that much while being loaded at a dock is he hearing a noise with it or is it just a bounce and that could be one of the leveling valves messing up.