Background:
2001 F-250 V10 4x4 SC
34k miles

Trailer:
18' Steel Deck Trailer 3700# gross weight, 16" wheel 2 5/16" ball
4800# Jeep on trailer.

I've owned the truck for about 3 months and had done about 200 miles of towing on it prior to this past week (never with this trailer). I never noticed any wierd habits before. Long story made short, I towed about 2000 miles with it from San Diego to Colorado and back. At speed (55-75mph) the back of the truck bounces/ vibrates. It seems to be sort of harmonic, in that it comes and goes, but doesn't have any pattern. The vibration seems to be speed dependent, not motor or drive train dependent. It will vibrate on acceleration and decel, constant speed or in neutral. What it felt like was bad pavement, but did it consistently without any regard for pavement condition.

I played with tongue weight a lot from very heavy to very light and it didn't make much difference. Tire pressure was set to max on both the trailer and the truck (305s on the truck, no lift). Nothing made any difference.

Anyone have any thoughts or ideas? All 4 truck tires remained in smooth contact with the pavement and weren't bouncing at all. The bounce was in the bed/body. Yes the trailer was vibrating as well.

Thanks.
Seth

 

In neutral , did you mean that when you were driving , you would shift the trans. into neutral , and still a vibration? I would do two things: First , make sure there are no belt shifts in any tires , trailer included. (You didn`t say if the truck vibrated with or without trailer?) The second thing would be wheel balancing , and check all the bearings.
On my old F150 , I had front shocks that were gone , and feather edged the rubber. It sounded like wheel bearings were gone , with a vibration. Turned out the tire was worn out of round because of the constant rise/fall of the front end , due to the bad shocks.

Just a few ideas...

Good luck

Sty

 

Our set ups are very similar, I also had a slight vibration problem. See signature for truck. My trailer is a 20 ft. Anderson equipment trailer with dual 7K axles. The trailer empty seems to be tongue heavy. I added a tool box on the tongue for chains, lug wrenchs, jack, ball mounts, etc., so this didn't help the trailer being balanced. I found by loading my tractor on the aft part of the trailer would keep the combination from vibrating. When moving the trailer unloaded the vibration would return. When moving my tractor with the bushog installed I had to pull it forward on the trailer to get the ramps up. So this made the truck squat and the vibration would return. I finally installed Firestone air bags on the rear and the squatting and vibration are history.

Also, had a friend years ago complaining of a vibrations/noise while towing his landscape trailer. His truck was a work truck and the trailer was never disconnected. Finally we discovered the ball/hitch was completely dry. They were actually destroying each other. It was so bad he has to replace the ball, and take a Dremel tool and smooth out the inside of the hitch. He now disconnects the trailer once a week to lubricate the ball with lithium grease.

Mark

 

Thanks for the input. It certainly seemed like the vibe was trailer related, especially since I've towed the same load on a different trailer with no problems at all. But.... I swapped the trailer onto a friends CC Long Bed PSD Dually and they didn't notice it at all. My guess is that the extra length and weight of the truck helped to equalize it.

Thanks.