Hello,
Can anyone give any advice on the following problem. I have a 2002 ford F250 with the 7.3L diesel, automatic transmission with 50000 miles. The truck is all stock except for the K and M air cleaner. When i pull my new 21 foot flatbed gooseneck trailer total weight 15000 loaded, The problem starts at 50 through 65 MPH. The truck starts to buck or it feels like the trailer is pushing the truck back and forth. It doesnt seem to matter if the road is smooth or has slight bumps. I dont seem to have the problem if the trailer is empty. I have been reading all i can find on this forum, And i know someone has the answer. The trailer is factory new, The hitch is manufactured by pop up and is located just ahead of the axle. Trailer towed level with truck, With no slop in gooseneck pin or hitch. I am down to having the computer REflashed, The only other thing the f250 is a short bed??
I have had several goosenecks before and have never experienced anything like this. All my other trucks were dullies
Thanks for any imput, link or phone numbers.

 

Welcome to FTE. Have you tried shifting the weight around on the trailer? Some trailers tend to jerk when their loaded a certain way. Since the trailer is new that sounds like an easy place to start looking.

How long have you had the truck? If it only happens at those speeds, can you monitor what rpm's you're having issues at, then shift into a lower gear and drive the same rpm range at a lower speed to see if the truck acts up again?

Do you have access to other trailers where you can test the same load, or possibly another truck to test drive your trailer with the load?

 

I agree with Chris above. I have expirenced that jurking motion You are talking about before, You can shift the load around some and get rid of a lot of it. My experience is to much weight on the hitch. You have to be careful to not take to much weight off and it starts swaying.

good luck

 

welcome to FTE the best forum on the net. There is a lot of great people on here who are welling to help if you just ask.

 

One thing you might do if you have no other options is set the trailer tongue a little bit high, like maybe 2" or so. At that weight if the trailer is leaning into the truck you are effectively trying to pull the trailer down over things. If it is higher, it tends to pull them over. Best example that is exaggerated is moving boxes with a hand truck. Trying to pop it over a curb or door way with the frame closer to parallel is by far harder than pulling it in an upward motion up and over the curb.

It is a stretch but if nothing else works out you could try it and see. Just remember you don't want it to high otherwise you'll load the back axle more.

 

Will it do what you are saying at 50-65 if you let off on the Fuel Peddle?

Did some searches and found other folks posting surges/bucks at a constant speed and these were the possible problems-> (TC slipping? Fuel Filter? Bad fuel, TPS? Leaking IC boots? CPS ?) I do know my 5th wheel tugs/pushes on me once in a while but I can tell it is the camper doing it because when the road is flat it is smooth sailing and If i let off on the power it still does it. If you are on good flat road, and it does it, it might(just guessing here trying to help) be one of the above from what i read.

Just some more food for thought.

 

If there is too much or too little pin weight the trailer pin will bobble up and down as the axles of the truck/trailer hit the irregularities in the road, truck hits it first and pushes the pin up, comes off of it at the same time the trailer comes across the bump, and you get the bump. A swift push of the go-pedal or using the trailer brake controller to load the brakes on the trailer usually helps

 

you will never be as happy towing with single rear tires after having dullies. But you can make sure you have load range E 10 ply tires with air at correct psi. this will help with side to side and hop make sure your truck has helper springs even some dullies don't have them. mike had good advice i like my neck a little high load trailer with only slight amount more weight ahead of axles . I have a freightliner day cab fld 120 on my 36 footer out in yard now no problems but i have a dual rear set up hope this might help in some way.

 

Get rid of that K&N filter too. It will mess your truck up.

 

Does the neck on your trailer angle into the hitch or is the top of the neck 90 degree's to the hitch. I hope you're understanding what I'm trying to say. Trailers that are 90 degree's to the hitch tend to flex at that joint. Thats why most newer goosenecks have the little 45 degree slope before attaching to the dropdown. My first gooseneck trailer bucked terrible, then I talked to a guy that builds trailers and he told me what the problem was. I replaced the trailer with the angled neck and the problem was solved. Hope this helps.

 

Might want to install some Air-Lift air springs- Helps balance and equalize the load while towing. Made a big difference on mine - Good Luck

 

Hmmm.... the first thing that came to mind was turbo surge.....

 

I would look more for a mechanical problem myself. Unless the neck on your trailer is not built very stout. Both of my goosenecks have straight necks and I have never experienced bucking. One is 14k and the other is 30k gvw. It isnt a dually vs srw issue, because 15k is not a problem behind a srw. The reason I say mechanical is you said it does it whether the road is smooth or rough. I just wonder if the TC isnt having issues?? Does it do it regardless of whether it is in or out of overdrive?

BTW, Welcome to FTE!!

 

Welcome to FTE.

I have had the same thing happen to me a couple times. I think you have too much weight over the hitch and not enough in the back of the trailer. I know that was my problem, but that was the only way I could haul the load. And it did it at the speeds you are talking about. I thought my seat was going to break off. lol

What are you hauling when this happens?

 

could be you have to much weight on the back of the trailer, not enough weight on the truck.