Rocking sideways motion, I have a 2016 ram 1500 bighorn and when towing my 30' camper I can feel a sideways rocking motion.

[crash68]

It could be that your previous 2011 had leaf springs whereas your newer one has coil springs.

One of the highlight changes for the Gen4 trucks starting in 2009 was the coil spring rear suspension. The 2500s didn't get the coil suspension till 2014 but the OP has a 1500.
Something has changed most likely on the OP's truck causing the rocking.

 

[huntergreen]

I’d change your rear coils to tuftruck progressive springs. Cheaper than buying a new truck. This assumes everything else is working properly.

 

[chri5k]

everything everyone has mentioned has been checked. I guess it's just a Ram issue. Maybe it's time for a change..

That doesn’t make sense. It all of a sudden became a RAM? What was it before, a Ford?
The OP said it was working fine until recently. Seems to indicate something has changed, worn out or broken. Vehicles don’t just suddenly stop working properly because of their brand.

 

[Maycraft1800]

I'm not saying it's the brand. I like Ram trucks but just can't figure it out..

 

[nlambert182]

One of the highlight changes for the Gen4 trucks starting in 2009 was the coil spring rear suspension. The 2500s didn't get the coil suspension till 2014 but the OP has a 1500.
Something has changed most likely on the OP's truck causing the rocking.

Ahh... you're right. I'm not nearly as familiar with the 1500 flavor.

I agree. Either something on the truck has changed, the load has changed, or a combination of them all.

 

[dennisok]

Move any weight possible that is behind the trailer axels to the front of the trailer. If you can't move any significant weight put a couple bags of dry concrete mix in front of trailer and take for a test drive. If it helps you have a weight and ballance issue packing your trailer.

 

[chri5k]

OP, any chance you can provide a list of what has been checked? Folks are trying to help but everything mentioned has already been checked. A list would allow folks to mention things that have not been checked.