Bouncing dually

I just purchased a 2018 3500 dually w/ cummins diesel. a couple of weeks after purchasing vehicle while driving to work at highway speed hit some bumps in the road and the truck started bouncing (twerking) uncontrollably. Had to practically stop in the middle of the highway to get it to quit. It is very sporadic in occurrences. I can drive the same stretch dozens of times and it won't do it, then out of nowhere it will again. any ideas???

Id run it by the dealer and have em look at a loose shock or spring hanger. I can't think of anything else. Except possibly too much air pressure

Blue Mule

Mechanical issues aside, one word: Oscillation !
Locally on a certain section of road my previous Chevy 1 ton (leaf springs/unloaded) would go into a crazy oscillation involving both ends, I tried braking and slowing down, speeding up to break the cycle and the only thing that worked was to slow WAY down.
These big heavy trucks have a " not so sweet spot" on certain road surfaces that make them act possessed !
I thought those days were over when I bought a Ram 2500 with coil springs. Not so fast... I still get oscillation on this section of road but it`s considerably less with this truck, especially after a installed the softer Thuren/King shocks 3in. system!
Here in the mtns we often carry about 250lbs of sand bags in the bed for snow/ice traction with a side benefit of smoothing out oscillation on these bad sections of road...
After ruling out mechanical issues try the sandbag trick (they`re cheap at Home Depot, Lowes, etc) and let us know how it works...
Also, I agree with Mc Broom, too much air pressure when empty is also a big contributor to the problem as well....

I keep my dually rears at 35-40 when empty.

Must have been the roads you were on. I have my dually for quite some time, and never had anything like that happen. Due to the harsh ride quality when unloaded, its not my daily driver though.

Your tires play into it as well..

Give this a reed

https://www.thurenfabrication.com/tech/death-wobble-in-depth.html

Ratket said:

Your tires play into it as well..

Give this a reed

https://www.thurenfabrication.com/tech/death-wobble-in-depth.html

Click to expand...

I re-read the Thuren link (also read it before I purchased their system) and I`m not so sure we are talking "death wobble" here!
As least in my situation, on certain sections of cupped/wavy road at certain speeds there is a pogo-like effect that (usually starts as hopping/bouncing in the unloaded rear) and progresses to include the front and finally the whole truck!
I added sandbags in the bed until I got the just right combo of weight that stopped the oscillation.
You can put the sandbags on the rear/sides of the bed which still allows almost full use of the bed.

"Death Wobble" is commonly found on 2nd & 3rd gen trucks.
4th gen it was corrected with a brace between the frame rails.

Blue Mule

1tons do that with empty loads.

The stiff springs are hard to control when there is nothing on them.


Sent while firmly grasping my redline lubed RAM [emoji231]

^^^ what U&A stated
If your not hauling anything, lower the pressure in the rear tires.

karl fields said:

I just purchased a 2018 3500 dually w/ cummins diesel. a couple of weeks after purchasing vehicle while driving to work at highway speed hit some bumps in the road and the truck started bouncing (twerking) uncontrollably. Had to practically stop in the middle of the highway to get it to quit. It is very sporadic in occurrences. I can drive the same stretch dozens of times and it won't do it, then out of nowhere it will again. any ideas???

Click to expand...

We certainly understand why this would be concerning, Karl. We kindly recommend bringing this to the attention of your servicing dealer if you have not already done so. Our team is just a private message away if any additional support is needed while working with your dealer.

Mark
RamCares

Rick Ram-jet said:

I re-read the Thuren link (also read it before I purchased their system) and I`m not so sure we are talking "death wobble" here!
As least in my situation, on certain sections of cupped/wavy road at certain speeds there is a pogo-like effect that (usually starts as hopping/bouncing in the unloaded rear) and progresses to include the front and finally the whole truck!
I added sandbags in the bed until I got the just right combo of weight that stopped the oscillation.
You can put the sandbags on the rear/sides of the bed which still allows almost full use of the bed.

Click to expand...

When the 2007 Tundra came out , there was an uproar about a freeway hop , shaking from the rear, mainly over concrete slab type freeways on west coast.
This only happened in certain parts of the country.

Keep in mind this is a softly sprung half ton

Chevy took advantage of this and made a video to show the uncontrolled bed and rear suspension motion on a test track that had bumps located to hit the frame resonance frequency of the Tundra

One of the reasons tundra never sold the first year target amount and thus had to hike prices to recoup investment in later years