Lurching/Jerking While Slowing down

C130 · 05-22-2013, 02:37 PM

Tow vehicle is a 2011 Ford F250 and pulling a Fuzion 322, 35 ft long. Truck pulled the toy hauler great with just a little sagging in the rear, not much at all. I installed air bags to get it completely level and after I installed them when I'm slowing down with no braking and foot off the gas pedal the truck seems to jerk or lurch back and forth if that makes sense. It didn't do it before installing the air bags and only does it somewhere between 20-40 mph. I've tried different psi in the air bags and usually run around 15-20psi while towing which keeps the truck level. Any suggestions?

chuck&gail · 05-22-2013, 06:07 PM

If it is a pull TT I suspect incorrect WDH adjustment. If a 5er, no idea.

schwalbach · 05-22-2013, 06:13 PM

just a thought, could the electric brake be interacting? maybe unplug lite cord and try a drive, wondering if the inertia arm is pulsing the brakes?

also something else to consider is the truck is level but is the trailer and are you getting bucking from the axles going over concrete seams? I believe if it is too high in the front it will buck off the back axle.

C130 · 05-22-2013, 06:43 PM

Quote:

Originally Posted by schwalbach

just a thought, could the electric brake be interacting? maybe unplug lite cord and try a drive, wondering if the inertia arm is pulsing the brakes?

also something else to consider is the truck is level but is the trailer and are you getting bucking from the axles going over concrete seams? I believe if it is too high in the front it will buck off the back axle.

I think you might be right about the truck being a little too high in the rear causing the front of the trailer to be high. The truck sits a little higher than it used to with the air bags installed. I was told to run a minimum of 10psi when not towing anything. Truck rides rougher also with the airbags at 10psi. I may lower it from 15-20 psi to 10psi while towing and see how it tows. The jerking was over a concrete road which we have a lot of where I live in Texas.

It is a 5th wheel. Never did it before the air bags were installed and almost wish I hadn't put them on. Is it normal to raise the rear of the truck a little with air bags installed if running any pressure in them at all? Would it really hurt to run them at 5psi or even less?

schwalbach · 05-22-2013, 07:27 PM

I never messed with air bags, but I would think to have just enough air to carry the ride height, but it appears you need at least 10 psi to keep the bag stretched so it does not get pinched or bottom out.

If it rode good before and now you are getting the bucking by raising the truck, you may have answered the question, change the fifth wheel height or pin box height by the same amount you raised the rear of the truck to get back to the trailer riding at the same height and it should be back to the same ride.

I once had a gooseneck trailer and it was riding very high in the front, way before I had a clue what I was doing, and it about threw me out of the seat until I lowered it to the right height for the trailer to ride level. this is what I am basing my comments on.

**hankpage** · 05-22-2013, 07:39 PM

The extra lift of air bags can limit the effectiveness of shock absorbers. They do not allow the travel length of springs that is needed for the shocks to work. At most times the air bags are great but under certain conditions can cause what you describe. Some claim adding storage tanks (Ping Tanks) and larger hoses will correct this. Under certain conditions it can be quite unnerving but I still prefer the benefits of towing level. JM2¢, Hank

warsw · 05-23-2013, 09:36 PM

Quote:

Originally Posted by schwalbach

also something else to consider is the truck is level but is the trailer and are you getting bucking from the axles going over concrete seams? I believe if it is too high in the front it will buck off the back axle.

I think "schwalbach" has hit the nail on the head.

I suffer from the same exact problem and for the same reason. I can't lower my hitch any because of clearance between the bed rails and the trailer so I'm working on a fix by raising the trailer 2" to get it close to level.

I haven't done all my homework so I don't know yet what is the best way to go about doing it but I hope to have some answers tomorrow. I'll let you know what I find out if you are interested.

C130 · 05-24-2013, 04:19 AM

I think you guys are right, thanks. Let me know, I am also going to lower the air bags a little. We are going on a trip today so I'll see how it tows. Truck appears level but I do think the toy hauler might be slightly higher in the front compared to before I installed the air bags. Guess I should have left it alone. I assume as long as the bags have at least 10psi it doesn't matter. The 10 psi was the minimum they told me to use.

TomHaycraft · 05-24-2013, 05:24 PM

I have followed this thread with interest. In April, I had an isolated incident. Stop and go traffic getting out of Austin and Oak Hill one Friday afternoon. Almost to a stop and it felt like someone bumped us from behind 3 or 4 times. Not change in engine speed, no change in feel of brake pedal, really startled my wife and I, to the point where I pulled off as soon as I could to check rear of trailer.

No damage, hasn't happened again. Transmission temp was about 202'. An earlier reply implicating the brake controller caught my attention. Like so many folks, I'm a bit nose high. I'll keep watching. Just now drove north from Austin about 3 hours, pulled and stopped with no issues.

warsw · 05-24-2013, 06:32 PM

Quote:

Originally Posted by C130

I think you guys are right, thanks. Let me know, I am also going to lower the air bags a little. We are going on a trip today so I'll see how it tows. Truck appears level but I do think the toy hauler might be slightly higher in the front compared to before I installed the air bags. Guess I should have left it alone. I assume as long as the bags have at least 10psi it doesn't matter. The 10 psi was the minimum they told me to use.

Well I went into town and talked to an outfit that builds trailers and does all the frame and suspension work for all of the RV dealers in this area (they were well recommended LOL).

What they suggested was to start by installing a lift kit on the trailer to get it level. They said this is really important on some 5th/Ws. They then suggested to haul it around for a while and see if this fixed the problem. They were sure it would either fix it totally or at least make a huge improvement. If there is still some trailer bounce going on after the lift they suggested maybe a new pin box but they said let's see where we are at after the lift.

They also said that shocks might help some but for the cost they usually don't help all that much.

I will let you know how the lift works out sometime next week.

Brantlaker · 05-25-2013, 05:15 PM

C130 did your truck come with a trailer tow pkg with a built in Break control? What is the GVW of the truck? Is it Gas or Diesel? A F250 with a 10,000lb GVW with a 6.2 will sag a bit as the first part of the Rear Springs are set for a smooth ride empty. Both my TT and 5er caused mine to sagged in the rear but they were level when towing. I talked to a Ford Engineer after I got my truck. That is what I was told ( I still have contacts at Dearborn). The 6.7 Diesel has hard springs and should not sag.

theeyres · 05-25-2013, 07:54 PM

This is no doubt a really dumb question: but why did you install in the air bags? If it towed great before, I would just let the air out of the bags and go back to the original towing. You mentioned "a little" sagging before air bags. A little would be no big concern to me. So what motivated you to put in the air bags?

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