Looking for possible ideas as to what is causing a vibration in my 2011 F150 FX-4 with the 5.0. The truck has a high speed, 70mph+, vibration-shimmy but ONLY when I'm pulling my small utility trailer. It doesn't matter whether the trailer is loaded or not. The truck does not seem to shake any other time. Before suggesting, I have pulled the trailer with another vehicle without the same vibration so I don't think it's the trailer. Any suggestions?

 

You are pulling a trailer at 70+ with tires and axle only rated to 65?

Pull the wheels off the trailer, get them and the tires checked for balance and out-of-round.

 

I agree with glc sounds like the trailer seeing its small it could be a wheel balance issue that or with that trailer and how its set up you maybe getting a tiny amount of trailer sway seeing how every vehicle has different effects on the same trailer such as hitch height and length etc... so there for I wouldn't suspect the truck seeing it don't do it when its disconected

 

Hmmm... what could it be??? what could it be???


maybe its the TRAILER

Like others have said, the tires are not rated for 70+ MPH.

OK, you tried it with another vehicle...
Did you pull it at the same speed with the other vehicle?
Even then, the hitch height is most likely different.
I'm guessing it wasn't an F150 so the aerodynamics are different.
Was it the same ball?
Even then, the hitch receiver is different so one might be looser than the other, thereby exciting a vibration at 70+ MPH


In case you haven't picked up on it yet, going over 70 with a trailer (especially a small trailer) is most likely your problem.

 

Its possible that the trailer is causing the vibrations

(Sorry just had to)

 

Oh Goodness here comes the trailer tire and speed limit police, Good luck Op! Get your fire suit on...

How dare you drive 5mph over the max speed of your trailer tires.. Im surprised the tires didnt burst into flames and kill a bus full of nuns

 

Coy, I learned this the hard way with a 5x8 trailer with a single axle and 13 inch wheels. It had car tires on it so I thought I could do 75. WRONG! I burned up the axle and it DID start a fire.

 

Thats why i go 15" wheels and tires with a 3500 lb axle on my 5x10... I had a cheapy lowes 5x10 with the 13" tires and a 2000lb axle and it was a flimsy piece of junk. Guess it just depends on the type of trailer..

I just get annoyed at some people (not you glc) that starts in with going over the speed rating of the trailer tires.. They make it sound like the second you go past 65mph something bad is going to happen and its not ture..

 

True, U-hual recommends 55 on all their trailers. I believe every one I have towed, probably close to a dozen rentals, has been 65-70mph

 

Id go nuts driving 55

 

Ya no kidding. but I really think they have the recommended limit for the total novice that has never towed before, and or probably have the trailer loaded incorrectly.

 

I'm not going to beat him up for pushing the speed limits of the trailer... its just important to know those limits so when you cross them and bad things happen (like a vibration or glc's fire) then you know why those things are happening.

ya ya ya, perhaps I beat him up some yesterday... but that was because he is saying that it can't be the trailer causing the vibration at 70+ MPH but yet all the signs point to the trailer...

 

Thank you for all the suggestions. For the record, the trailer while small, does have 15" tires and a 3500# capacity. It has been pulled by another PU without the vibration. Although I haven't completely ruled out the trailer as the problem, I plan to load the bed of my truck and see if that causes the vibration without the trailer. I'm wondering if a bent axle shaft could be to blame and is only noticeable under load. Thoughts?

 

The receiver on your truck may be slightly larger making the hitch fit looser. I use a screw in hitch bolt to keep it tight. The trailer coupler may fit loose on the ball, tighten nut slightly on bottom of coupler. Shake trailer drawbar to check.
Pull without tailgate as a test. Wind around your truck may strike trailer different than an other.
Tire balance would be first on my list also.

 

im going with this