Vibration when towing

[Armypilot]

I am towing a 7500 lbs tandem axle trailer with a diesel tractor with loader on it. I have a weight distributing hitch and use it. I get a vibration that is on for a second and a half and off for a second and a half that vibrates quickly through the whole truck. This happens in drive under power and when coasting in neutral telling me it is not drivetrain. It seems to stop if I squeeze the trailer brake controller and apply trailer brakes only.

Is this maybe due to where my load is distributed on the trailer. Lack of tongue weight or not enough? I tend to put my tractor rear axle over the forward set of wheels with the tractor and loader facing forward.

It is an annoying vibration, makes the passenger seat back shake when no one is in it and reverberates through the truck.

With no trailer truck is perfect.

Any ideas?

[FINE69]

Maybe you have something wrong with the trailer. Could be a brake or bearing problem, being that it stops when you push the brake controller.

[Armypilot]

I didnt even think of that, the trailer has about 600 miles on since new. And it is less than a year old. I'll have to look into it.

[Down South]

It could be a balance problem with the tires on the trailer.

[Armypilot]

I drove the trailer unloaded with the weight dist hitch bars installed, same vibration but worse.

[CaptRon]

There have been threads on this problem before and I believe that the inclination of the rear axle to the driveshaft was the problem.

Nice Day Job btw.

Capt Ron

[cdacaraudio]

i get this problem only when towing a friends trailer witch sounds a lot like what u have.. we noticed that the more u put the weight on the tongue the better the ride.. now i towed this trailer with and with out brakes so it was not the brakes, also towed it loaded and unloaded and yes it was much worse unloaded. now i tow my bosses work trailer and no mater what i never get this problem i think it has something to do with the trailer axles. i don't use any weight distribution hitch and if u note my truck is a dually.. i tow any where from 2000lb's up to 14,000lb's and don't get problems only with that one trailer.. my thought is maybe one of the axles is not aligned with the other and its causing the tire to bounce a little.

[SteveRacer]

[ QUOTE ]
There have been threads on this problem before and I believe that the inclination of the rear axle to the driveshaft was the problem.

[/ QUOTE ]

Capt Ron might be right ... a racing buddy of mine had the exact same problem, and after several visits to the dealer they replaced the driveshaft and adjusted the angle of the diff housing. Now it only does it empty instead of loaded with trailer.

We have almost identical trucks and trailers, and I've never had a problem. [img]/ubbthreads/images/graemlins/shrug.gif[/img]

HTH-

-steve

[Armypilot]

Ok here is some more pertinent info maybe.

The trailer even with the load is about 3-4 inches high in the front due to my draw bar does not drop enough. So when I add the equalizer bars it is even more nose high. After re reading the hitch instructions it seems important that the trailer is level.

Could that be inducing my vibration? The trailer not being level?

[CaptRon]

That would be more conducive to sway than vibration.

Capt Ron

[CascarFan]

[ QUOTE ]
Could that be inducing my vibration? The trailer not being level?

[/ QUOTE ]

I don't know about inducing a vibration, but you'd be putting a lot more weight on one axle vs the other and if you're loaded to the max, risk blowouts on the overloaded axle, I would think???

[HenryE]

pilot

You are definitely running a lot more weight on the rear axel if the trailer is nose high.

[Armypilot]

Well I have ordered an extended drop bar that will correct my geometry. After that is correct I will then go to other issues if the vibe is still present.

Thanks guys