Drivetrain slipping?

So yesterday I was headed out to a job pulling my equipment trailer which is pretty heavy and the route includes some hills with up to 7% grades. Going up one of those hills at medium RPM but near full boost the truck bumped like I had hit a small pot hole, but only once and I was going in a straight line so I should have hit with both tires if that was in fact the case. Then it bumped again and a few more times on the way out and the way home. It did this in both 3rd and 4th gears with RPMs ranging from 2500 to 3500rpm. The bump reminded me most of when the chain on my bicycle stretched out and would occasionally slip a tooth on the sprocket. No error messages so far so no clues there. This is a little premature to asking questions but I really don't want to run to failure and end up broken down with a heavy trailer on a 7% grade.

Has anyone had a problem like this before? What did you do to fix it?

My truck is a 2016 F150, 4WD, 3.5 Ecoboost with 6 speed transmission. It could the engine, transmission or transfer case, maybe even the rear axle.