[AmeriLite21]

Abner,

The Ranger had factory tow package with transmission cooler. It was tow rated for 5080 lbs. We didn't weigh the trailer, but it came out of the factory at 3334 lbs. and we only added about 250 to 300 lbs. in equipment, including two full propane tanks. We never fill the water tank until we get to the campground and empty it before we leave.
I had turned the overdrive off.

It should have been able to pull the trailer no problem. I just think there was something in the transmission waiting to happen and the hills and 35 mph wind made it happen. Just before it started slipping we were doing 55 at 2500 to 3000rpms for about 30 miles with no indication of anything.
Then the speed just started dropping and the rpms went up to 3500 to 4000. When we pulled off the 4-lane onto a 2-lane it was going normally again. Then about 25 miles later it started slipping again and shifting hard.