Truck bouncing with load

[That Guy]

I just pulled in from my 11 hour drive from Chattanooga with 15k in tow. I have found that the truck bounces in a resonance when on a poorly paved interstate while under throttle, no issue when coasting. If I let off it stops, back on and it starts again. Slow down to about 35-40 and it goes away, not really feasible on a 70mph interstate as the bad surface may go on for miles. 

The best way to describe it is feeling like the shocks are completely gone, but it only does it on very specific buckling highway. I can hit large bumps and bridges, and no bounce or anything consistent with bad shocks. The speed at which it happens is based off how far apart the buckles are, usually about 4-6 times a second at 65mph. Uphill/downhill has no effect, only road surface and throttle, exhaust brake does not cause it.

 

Because it only does this when under power and with a heavy load, I'm thinking axle wrap may be an issue. The more throttle applied, the worse it is. 

 

Ideas? In my mind, if it is axle wrap, maybe track bars would fix it. Maybe the shocks aren't strong enough?

[Mopar1973Man]

Are you hauling heavy commonly? I would consider air bags possibly to aid in suppression of the bounce. I would consider having a in-cab controller for the air bags so you can inflate or deflate as the road condition require. 

 

We've got a few old instates and concrete highways too. I've ran both Rancho's and now KYB shocks. Both are good shocks and help with bounce some what. Most here will jump for the Bilstein's shocks. 

[Me78569]

I'd be trying shocks first as they are likely due for replacement and they are cheap compared to the other things.

[Doubletrouble]

 I vote shocks as well. The internal pistons/seals could be worn where they ride most of the time while going down the road. A larger bump would push the piston out of this worn area and the shock would dampen better because of the better deal.

[Mopar1973Man]

I was talking to a gent today about this and he was suggesting a air bag system for people that tow heavy constantly to have a independent air controller for left and right in the cab. Makes the best towing when you long hauling. You can adjust on the fly to smooth out rough patches. 

 

For people just once in awhile.. Shock would be the first stop. Kind of like myself I tow but not daily. Hence why I don't have air bags...

[NIsaacs]

What were you towing/load? Most goosenecks will do this, sometimes even empty. I have never been able to put a finger on it. It is not the shocks nor the truck, it is the trailer. It bothers my dually (air bags) worse than my '01 Dodge (no bags). I kind of figured it was because the trailer does not have shocks. The tandem axle/equalizers spring trailer is worse than the torsion but the torsion will do it too, usually when empty.

[That Guy]

I'm actually considering the 4 wheel full air ride system from Kelderman. My mother is wanting to buy another truck to ride around town in because the dodge beats us up going to the hardware/feed store. $7500 suspension upgrade is cheaper than another $30,000 Chevy. 

In the mean time, I'm going to try some shocks. At 90k on the clock, they can't hurt. This last trip was brutal.

 

It was a goose neck, neighbor says he thinks the mounting location in the dodges needs to be further forward. There is a brace in the bed about exactly where he likes to mount them. The ~3" difference between the two spots makes all the difference according to him. 

[Me78569]

Should be right over the rear axle or an inch in front of.  

 

 

My oem mount if right above the rear axle.  

Edited September 29, 2020 by Me78569

[Royal Squire]

B&W makes a 4” extender(made to give more room in short bed when towing gooseneck) but would allow you to move ball forward to see if that helps. Assuming you have a B&W gooseneck hutch.