rv and truck sway

[Jakenbear]

Not sure if anyone has this experience, but I have had this happen the last two times we were out. We are towing a a 42 ft. Bighorn, grossing out about 16,000 lbs. with a 2018 Ram 2500 diesel. When starting up and accelerating, around 40 mph, the trailer and truck start to sway. By backing off the gas pedal, it seems to stabilize and drive OK. I believe that because of the load, the front end of the truck may be coming a bit sloppy on the road and causing the sway. I thought of putting air bags on the rear of the truck to level more, but not sure. Does anyone have any ideas, or had this happen to them. All yo9ur ideas are appreciated.
Thanks
Jakenbear

 

[MTPockets]

Several questions: what is your pin weight? Truck payload capacity from door post sticker. Have you changed truck wheel size from stock?
Airbags won’t change any load ratings. My immediate instinct is that you need a 3500 series truck and dual rear wheels.

 

[Jakenbear]

Not sure of pin weight. Ram specs indicate I can pull a little over 17,100. No tire change in the last year. Nothing has really changed sine I bought the unit in 2018. Perhaps I have a larger cargo load these last two times??

 

[JohnDar]

Good bet that the pin weight of the trailer is a bit heavy for the rear springs and it’s causing the front to lift on takeoff. Have you had the truck and trailer weighed? The pin weight on the sticker isn’t 100% accurate after you add all your stuff into the rig.


Sent from my iPad using Tapatalk

 

[MTPockets]

Not sure of pin weight. Ram specs indicate I can pull a little over 17,100. No tire change in the last year. Nothing has really changed sine I bought the unit in 2018. Perhaps I have a larger cargo load these last two times??

Pulling, is only one factor, but the more important is the payload capacity of your truck. You need to know also your trailer total pin weight, which is only accurate when weighed fully loaded with all your gear. I’m guessing your truck payload is ‘maybe’ 2600 lbs, but check your sticker to be sure. I would suspect you’re overloaded. Nothing you can do except get a heavier truck.

 

[JohnDar]

On our (former) BH, the trailer was 14575 with most of our stuff in it. Pin weight was actually measured (at 2011 rally) as 2950. But then, I had a 3500HD dually that could handle it.

Sent from my iPhone using Tapatalk

 

[danemayer]

Nothing has really changed sine I bought the unit in 2018. Perhaps I have a larger cargo load these last two times??

There's the possibility that exceeding payload spec, if you have, may have put excess wear on the rear axle and other components. You may have something your truck dealer needs to investigate.

 

[centerline]

one will need the actual weights, NOT a guess or estimate... pin weight, the trailer axle weight, and the weights of both axles on the tow vehicle, and where the kingpin/hitch center is located in relation to the rear axle of the tow vehicle, to help figure out whats going on...

with a 5th wheel set up, there are only a couple things that can contribute to swaying, which is why they are so much safer than a bumper pull trailer.
the first couple things can be ruled out fairly quickly, which is, worn pavement and/or, a stiff side wind can cause the rig to sway...

other factors are, too much weight behind the trailer axles can cause swaying, or if the springs under the trailer are too light for the weight of the trailer, it can sway...
and the 5th wheel hitch to far REARward can cause swaying....

also, if the kingpin is excessivly far forward, or excessivly high, but this would be a very UNnormal set up..

a "properly" loaded 5th wheel trailer is fairly stable in all directions, so as long as the suspension bushings and shocks in the tow vehicle are in good condition, it would be difficult to get it sway...

 

[NYSUPstater]

My $.02 as well, your overweight on truck as others have stated. 1 ton SRW maybe just marginal (little to no wiggle room), so might want to consider a DRW. We thought our '15 F350 SRW would be our last truck.......well it was till we got the new coach. Pretty much maxed the 350 out and due to trip we were going to take (making this a short story), ended up getting a DRW just 3 1/2 years later. Didn't want to, but can tell you for towing, all the difference in the world. Wife even feels comfy /better with the DRW towing while relieving me for a spell or 2.

 

[hoefler]

My bet would be you have a short bed truck, the pin is either on center of axle or set behind axle. When accelerating, you are unloading the front axle. The hitch needs to be forward of axle for proper setup, 4" is recommended for proper loading of front axle.

 

[CoveredWagon]

My bet would be you have a short bed truck, the pin is either on center of axle or set behind axle. When accelerating, you are unloading the front axle. The hitch needs to be forward of axle for proper setup, 4" is recommended for proper loading of front axle.

If this is the case adding air bags to help from,unloading the front axle might help

 

[centerline]

If this is the case adding air bags to help from unloading the front axle might help

or, it could make it worse....
if the kingpin placement is too far rearward, adding air bags wont do anything for the front end, but will only help with leveling the truck.

if the "load" is directly over, or behind the "reaction point", no amount of suspension will cause any more weight to be transferred to the front end...

with some of these newer trailers with their higher weights, a kingpin setting of 1" forward of the rear axle is a bit shy of the mark... 1.5 to 2 inches would be better for proper weight distribution, and in my opinion, safer, ESPECIALLY if one has a long wheel base tow vehicle, such as a crew cab...

a heavy trailer coupled to a short wheelbase tow vehicle has its own issues that just has to be dealt with and worked around, because short WB vehicles will always be more susceptible to sway than long WB vehicles will..

 

[jbeletti]

This may not apply to your situation but tossing it out there just in case.

I had unknowingly exceeded the GVWR of my RV (a travel trailer). In doing so, the rear axle had lost its camber. As a result, the inside tread on the rear axle tires began wearing excessively (toe-out). Before I knew I had an issue, I noticed that towing was a bit more sketchy than normal.

I pull this 31' travel trailer with a short-bed F150. What I was experiencing was more-than-normal trailer sway. I had a hard time keeping the trailer straight. This was while towing at 55-60 mph.

Well, turns out that this tire toe-out from loss of axle camber makes the trailer tow squirrelly.

Here again, you may have inspected your axles and tires and found the axles to have an upward arch (good camber) and the tire sidewalls to be very perpendicular to the road (no toe-out).

 

[Kathi-27]

had 2017 bighorn 3870 fb 3500 single rear wheel rear tires where overloaded and caused sway. need dual rear wheels with that size unit

 

[Jakenbear]

Thanks to all for your thoughts and ideas. The truck is going in the garage tomorrow to check the springs, suspension, and hitch bolts etc. If that checks out the Big Horn is going to the rv repair shop to check the suspension, wheels and tires as well. The hitch is centered over the differential, all tires have been check for proper pressure. Will also check the camber at the shop. We have had this rig for 2 1/2 years (it's a 2019) and have never had this problem before. Will let you all know how this turns out in a couple of weeks.
Again, thanks for all your suggestions
Jakenbear

 

[danemayer]

Thanks to all for your thoughts and ideas. The truck is going in the garage tomorrow to check the springs, suspension, and hitch bolts etc. If that checks out the Big Horn is going to the rv repair shop to check the suspension, wheels and tires as well. The hitch is centered over the differential, all tires have been check for proper pressure. Will also check the camber at the shop. We have had this rig for 2 1/2 years (it's a 2019) and have never had this problem before. Will let you all know how this turns out in a couple of weeks.
Again, thanks for all your suggestions
Jakenbear

Circle back and let us know what you find.

 

[carl.swoyer]

Thanks to all for your thoughts and ideas. The truck is going in the garage tomorrow to check the springs, suspension, and hitch bolts etc. If that checks out the Big Horn is going to the rv repair shop to check the suspension, wheels and tires as well. The hitch is centered over the differential, all tires have been check for proper pressure. Will also check the camber at the shop. We have had this rig for 2 1/2 years (it's a 2019) and have never had this problem before. Will let you all know how this turns out in a couple of weeks.
Again, thanks for all your suggestions
Jakenbear

Have you inspected under the fifth wheel and looked for broken leaf springs or broken hangers. Maybe a broken weld.

Sent from my moto z3 using Tapatalk

 

[Jakenbear]

Still have not found out reason for sway. Trying to determine if I am overloaded. My pin weight is 2716, and the GVWR of the Big Horn 3760 is 16,000 and dry weight is 13,240. My 2018 2500 Ram with 6.7 Cummins can tow 17,000. Have not had opportunity to weight the unit yet, but am trying to shift some weight toward the back and not hauling full tanks of propane. Any more thoughts?
Thanks,

 

[carl.swoyer]

Still have not found out reason for sway. Trying to determine if I am overloaded. My pin weight is 2716, and the GVWR of the Big Horn 3760 is 16,000 and dry weight is 13,240. My 2018 2500 Ram with 6.7 Cummins can tow 17,000. Have not had opportunity to weight the unit yet, but am trying to shift some weight toward the back and not hauling full tanks of propane. Any more thoughts?
Thanks,

Travel with full tanks of propane and 1/3 tank of fresh water. A picture of the fifth wheel hooked up to the truck would help.
When I towed with my 05 2500 cc lb srw I ran at 80 psi. I also had an extra leaf spring put on.
I never towed faster than 63/65 mph. .
I really think you're in the wrong truck.
Since going to a dually it's like night and day.
In my 05 I never experienced swaying.

Sent from my moto z3 using Tapatalk

 

[cookie]

Sounds like your going in the wrong direction.
One of the causes of trailer sway is not enough pin weight. Changing trucks will not help that.
If you haven't had your rig weighed you cannot guess the pin weight.

Peace
Dave