Gooseneck causes truck bounce?

[FlaDon]

Truck's and trailer's wheelbase equal to the section of concrete between expansion joints causes it. There are some bridges in GA, SC, and NC that make you think you are a Porpoise. Different lenght trucks and trailers respond at different speeds or section lenghts. Some times you feel you want to

 

[Slice]

It happens in Texas too. beat you to death

 

[whistlepig]

I do know that the mounting location of the fifth wheel hitch in the bed of the truck is critical. I had one installed in a 1979 pickup. The installer said just a little bit too far forward or too far back can cause problems. I am sure that is not the problem in your case.

 

[Skyco]

It is the road joints...I've had it happen in vehicles without trailers at certain speeds on certain roads. Part time job I had in 1970 had a Ford Pickup with the old twin I-beam suspension, there was a bridge on the interstate going into town. Every time anyone went over that bridge in that truck it would start bouncing until about 2/3 of the way over the bridge the front suspension would go nuts and oscillate back and forth so hard it would almost jerk the wheel out of your hands. Once it started doing that you had to almost stop, down to 1 mph or so to stabilize the truck then go again. It was quite a topic in the shop

Back about 1990 was going out west with a tent railer in tow behind my 1987 Ford Clubwagon. One of the interstates there had the same effect with the bouncing, every 20 miles or so the back door of the van would unlatch and pop partially open, necessitating a stop to shut it. Never had it happen anywhere else in 100,000 miles on that van!

 

[whistlepig]

I think it is the expansion joints also. Sometimes they are cut just right to get the truck and trailer bouncing.

 

[RobertN]

That is funny, because the Texas roads I was on from El Paso to Corpus Christi, were better than the roads in California. Even in construction areas.

I caught a spot on I-80 going from Sacramento to the Bay area, where it was a 55mph construction zone. They had a sign that said "Bump". Even though I was going a bit slower than the speed limit, it felt like it was about to rip the 5th wheel from my truck. Never had that in Arizona, New Mexico, or Texas during our journey to Corpus Christi.

Per the OP, there is a strip of concrete freeway in Sacramento, that makes my truck bounce all over when empty. It is OK when I have the 5th wheel loaded. Funny thing is, is my old Jeep was as bad as the truck, but all of our cars were OK. Seems the trucks long wheelbase, and the Jeep's short wheelbase, oscillated similarly. Seems the truck hit every other, but the Jeep hit every, expansion joint at the right frequency.

It happens in Texas too. beat you to death

 

[sandman2234]

To fix this, add a slider to your front axle so you can spread the two axles apart for a more even ride. You will get some but you can change the harmonic effect by moving just one axle forward.
Not an easy home-shop modification.
David from jax

 

[FlaDon]

To fix this, add a slider to your front axle so you can spread the two axles apart for a more even ride. You will get some but you can change the harmonic effect by moving just one axle forward.
Not an easy home-shop modification.
David from jax

The bridge on 9A in Jax can do it too. If you catch it on a day when it isn't down to a crawl due to the bridge being painted.

 

[Chris611]

Well, glad to hear that it happens to other people. I was worried that something was setup wrong on my truck or the trailer.

Later

 

[DanD78]

I agree with all that said it has to do with wheel base and expansion joints. I recently traded trucks and where the long bed extended cab would bounce the long bed 4 door will not. But then again there are now places where the 4door will bounce where the extended cab did not.

Those guys went to school for 4 years or more to figure out how to put the big bumps before and after bridges and make the wheel base match the joints in the road.

Dan