On my 2019 (too soon to have worn seat hinge bushings), I discovered the thumping rattle in the rear was caused by the top mounts of the shocks being too large a diameter. This left next to no clearance between the top of the shock mount and the body! The sound it made just rolling down the street was unbearable! My mechanic and I traced to to the shocks when we put it up on the lift. To simulate bumps, I started doing pullups on the rear frame near the stabilizer bar. My mechanic could hear the slight popping noise that was transmitted though the rear cargo area as a "thumping rattle". When he wrapped his hand around the Chrysler OEM factory shocks, he told me that there is an unnatural popping vibration. He noticed the top shock mount was damn near touching the body. We assumed that the bushing had some compression under load as the vehicle slightly bounced which was causing the tapping on the bottom of the body or floorboard. We removed both shocks, and as I backed it down the ramp, the back end was bouncing like crazy as the shocks were now off. There wasn't a peep. The noise was gone. We ordered some mid grade Monroe shocks. When the parts company dropped them off, we observed that the diameter of the top mount was way, way smaller than the diameter of the OEM shock absorber!! After installation, I drove away and the quiet ride home was so enjoyable. Who would have ever thought that Chrysler/Dodge could screw up so badly? Hell. Dodge and Carmax couldn't find the noise after two appointments each! Carmax wanted to remove the evaporator case this upcoming Tuesday as they said the noise was coming from there. Before heading to my mechanic for an oil change and another attempt to find the source of the sound, I crawled into the back and rocked the van. Now, the sound was coming from the other side as well. Both shock mounts at the rear, rubbing the body above explained it all! Thank you L. Strom as I will be keeping a close watch on those seat hinge bushings!!! Needless to say, I called Dodge and Carmax to tell them to be on the lookout for this problem. By the way, l also have a vibration in the seat at 65 mph. The wheel balance took care of the vibration at the steering wheel and the rotors are fine. I believe like L Strom, I will be replacing one of the half shaft front axles. It is a shame to have to do all this on a 2019 with 36, 000 miles!!!