Please help me identify 5th wheel towing issue.

Super_Dave, feels like its coming from the back and I have suspicions that it might be somewhat to do with the trans. I only have 26k on the truck. Was going to have a full fluid change out to synthetic but $300 is pricey. ependydad, not ready to ditch the Andersen yet. I love the fact that its easy to hook up and lightweight.Want to exhaust all possibilities first. I plan on getting the rig weighed to help troubleshooting.