When I am pulling at speeds of 50-70 mph the truck will intermittenly jerk as if the trailer is braking on its own.  The jerkingness has different degrees of jerking, from moderate to just about severe! Keep in mind this is intermittent jerking. I have had the electronic brake controller and truck checked and they are working fine.  I have visually inspected the connections to the plug(plugs into truck) and made sure the break away brake switch is frimly seated.  The tires are new and can't believe the tires have ANYTHING to do with how extreme this pulling, jerking issue is. I have only had the trailer out 2x since I have owned it and I need to get this problem fixed before I take it back out--especially at high speeds.  Does anyone have any clues to help me figure this one out??  Could the outlet in the bed of the truck be 'bad' and causing this?  What would make my brakes come on without me pushing on the brakes?  Thanks for any advice.

Check for shorts between your brake controller and the truck; that's what mine was when this happened to me.

Did you take the trailer plug apart and check inside for a jumper across any of the other terminals over to the blue brake wiring terminal. Those little strands of copper wire can break off and float around inside the plug doing some amazing things sometimes...

You have a very good memory!  I was the one who submitted an article about the same issue awhile back.  Everyone talked about it being the tires and I can't believe the tires are causing such a strong back pulling issue.  And as far the road conditions go, the highway was not causing this either.  This pulling sensation is backward, not forward and up and down.  I also checked my goose to see if it was rocking or jumping and everything was fine there too.

I appreciate your .02cent--it is worth more than that to me.

Nothing seemed to make it stop--not braking or slowing down.  Although it would finally go away if I would either slow down or speed up.  And sometimes that didn't work either.  I did not notice this issue when I was on two lane state roads or highways going at speeds of 55.  If it was just me by myself experiencing this problem but I have had two other people with me and they can attest to the severity of it.  And we made note of the road conditions--which one time were newly paved. 

I appreciate your input==thank you.

I see F450.  Is that a Desiel?  You should have your EGR valve looked at.  It is a common cause of lurching on the highway under load.

I changed mine last summer (5 minute change) and was shocked at the difference.

I now want to carry a spare for a quick change when on a long trip.

So you are thinking the diesel truck might

Just an f.y.i., found out the F450 diesel 7.3 liter does not have an EGR valve.

But did take trailer to an RV place today and had wiring checked and everything 'looked' good.  They did ask me if I took the overdrive off when pulling and I said no.  So this could be the problem.  zit has never been a problem before but they said that having it on is hard on the transmission.  So all I know to do now is drive without the overdrive on. 

How about that fuel filter... How long and how many miles since it's been changed..?

Yea EGR valves affliced 2003 and up.

Try this web site

http://www.powerstroke.org/forum/ford-03-07-6-0l-powerstroke-forums/

You can trouble shoot the problem to specific areas fairly easily. By towing on varying road surfaces, some smooth, some with expansion joints, you can discern whether or not the interplay between the trailer and truck is causing the jerking. If there is no difference, then suspensions, hitches and wheel base concerns can be eliminated.

To determine if brakes are involved, travel the same roads with the trailer plug disconnected. If the trouble persists, it is not an electrical brake issue. However, if some of the mechanical brake components have failed, such as the shoe retract springs or an adjuster linkage, a brake shoe could be temporarly engaging the drum assembly. This can usually be determined by having someone walk beside the trailer as it is slowly being towed. An intermittent, metallic rubbing, or chaffing noise will occasionally be heard.

With a drive train problem, you have three areas of concern. Motor, transmission and axles. Any one can cause the problem. The axles are usually trouble free if they are properly lubricated. A friend of mine experienced some drive train jerking prior to his rear axle locking up. The rear differential cover had rusted, allowing the gear lube to escape, and the gears to eventually run dry. On some of the older positraction gear units, the clutch packages would act up as they wore.

Because all modern engines and automatic transmission are commonly linked by computer controls, it's more difficult to determine which one is at fault. Some problems can only be determined, by whichever service department has the most skilled diagnosticion and equipment.

Once all the easy determinations are made and no fault has been found, it may be time to call in the experts.

Thanks.  I will try the pulling slowly while someone walks along side trailer to see if they hear anything.  The more I think about it, if the trailer brakes were seizing (for whatever reason) wouldn't I notice wear or dust on the tires?  So far they still look good.  My actual pull miles on it are right around 330 miles.

I would have to unplug the trailer from my truck and go down the interstate to duplicate what I have previously experienced.  That sounds a bit scary to not have any brakes or lights to trouble shoot a question of electrical problems. Supposedly, the electrical has passed all inspections.

I have an appointment with Ford next week to run a diagnostic ? on it and check all fluid levels. 

I want to get things resolved so I can safely hit the road and then the trails!!

Thanks for your insight and advice!