Have an '03 HO 6spd positrac (or whatever you call these 2 wheel drive rear ends these days). Also have a 2% grade up my drive which is covered with gravel at varying depths (zero to 6"). My fault, I should grade it, but that's life. I also have a 25' gooseneck trailer.

When backing up this rig up my drive, all that diesel torque, if the truck tires begin to spin, the rear end will start bouncing up and down to the point that I've actually shook things around in the truck bed. I've also noticed this will happen not only in reverse, but going forward, but not as bad.

From the tracks up the drive I've left, it appears like first one tire breaks loose, then the other, then the original, then the other, back and forth, causing said rear end bouncing.

Problem is, I have to make a bit of a run up the drive to get the entire rig to its resting place on my lot. It is, however, neat to hear that diesel turbo wheezing after I let off the clutch ;-).

Been all over the net, can't find anything on this. If any of your rigs display this behavior, please let me know. Otherwise, I might have to trade it in on a 4x4.

 

4x4s do it too sometimes. My 98 4x4 dually was horrible in the snow. That rear would start bouncing around to the point where I thought I was gonna break something. My buddy's 01 4x4 did it a little in the snow last year but it was not as bad as the dually. Do a search on the topic. Someone gave a detailed explanation on it a while back....

I have not had that problem with this truck so far.....

 

its called power hop the tire grips then slips causing it to bounce all of them will do it however with 4wd engaged especially using 4 low it will be greatly reduced as you have a heavy front end sitting on extra driving tires. nothing big

 

Try experimenting with higher and lower pressures in the rear tires.

 

Actually it's axle wrap. Very common on high hp leaf sprung vehicles without traction bars or ladder bars. As you apply torque to a leaf spring it begins to wrap itself into an "S" shape. When the combination of torque and spring wrap load exceed the available traction the tire breaks loose and the spring snaps back to original shape causing the vehicle to momentarily "hop" or bounce. Hence the term "wheel hop".

In thier efforts to give us a softer ride when unloaded the factory went to a longer and softer main spring. This coupled with the massive bottom end torque of the Cummins sets the stage for the worst case of wheel hop I've ever seen in a truck. Gravel and loose substances are the worst and really make this problem rear it's ugly head. A 4 link rear end, such as the Kelderman air ride, or ladder bars is the only way to overcome it for good. Without spending a ton of money the best you can do is what you are doing right now. Take a run at it and use just enough throttle to crest the top of the rise, or have you're driveway paved to give the truck the traction it need to torque the load up the hill.

Then again, I have a soft spot for the 4x4 Duallies.

Sorry for the long post, hope this clears up some of your questions...

-Richard

 

Yeah, I have experienced this only on gravel roads that are real bumpy and that have grooves where everyone else hopped along. It's more noticable when I'm on a bend and just skip and slide the rear end around. I contribute it to my speed around bends, if I slow it down, it becomes very minimul. When it's muddy, on the same road I usually engage 4X4 mode and never experience that hop. My 2 cents...

Gypsy..excellent post now I KNOW WHY TOO!

 

I'll try adjusting air pressure. I normally run 70 all around, loaded or not. One thing I tried before I posted, there is a 3/4" steel pad, from the factory, that sits sandwiched between the axle pad and the first leaf spring. I removed mine to get a bit of that giraffe-a$$ look gone. Still hops just as bad. I'm going to try to rectify this problem over time. I'll keep yall posted. Thanks

 

I did forget to mention one thing. Ladder bars or traction bars will limit or eliminate the problem 99.9% of the time.

-Richard