Truck Bounce

Simple and inexpensive suggestin would be to replace all the shocks...cab and axle ones. But the problem is probably something more. Have the driveshafts been checked for out of balance or out of round (also check the carrier bearing for play). Not to knock what you have done, but many shops have become "parts changers". I would take the truck to another shop or two to get more opinions.

 

It sure would seem like a driveshaft problem or U joints, we had a pickup truck do that same very thing, kept getting worse and we finally ended up replacing the drive shaft and U joints, hope you get it fixed and please let us know how you make out.

 

What kind of rear suspension do you have?

 

Tandems parellel to the frame? to each other? Maybe have a good truck alignment shop check it out. Also, don't forget the driveline phasing, not just the balance.

My suggestion would be is to find a shop that has a VIS machine. MHC Kenworth in KC,MO has one. Unfortunetely, that's the only one I know of. But I'm sure if you call around, someone will know. Those who have and can operate the VIS machine correctly should be able to quickly diagnose the problem. That machine is expensive, but saves lots of time.

 

Try draining a little oil out of the front diff and see if it has metal in it. I had a KW that was doing that for about a year and getting progressively worse. I spent a bunch of money on shocks and bushings, drivelines rebalanced, tires etc. One day the front differential blew up bad enough to knock a hole in the case. After we got it fixed, the truck was smooth as glass. The nut had backed off the inside on the power divider and was letting the pinion walk back and forth. I think it was binding up with the ring gear and causing the hop. Anyway nothing seemed bad when looking at it from the outside. When I drained the rest of the oil out it was the prettiest metallic brown you ever saw. Just an idea for you.

 

From your description, it sounds like you have what is called a Reyco rear suspension. They generally don't use shocks