The front left caliper did this on our trip last summer on our 2000 FW/E350. It was pulling hard to the left, until the brakes were applied, then it would jerk to the right. It took a lot of power to pull short hills too. When I stopped to check it out, yowsa was it hot.
We limped it to a Ford dealer 2 miles back, where they promptly told they didn't work on motorhomes. I stated it was juts a van... then I suggested the Chevy dealer just down the street would probably help me. At that point, he went in & chatted with the service manager. Yep, they would do it.
As it was 3:30 in the afternoon, they pulled a guy off another job & had him evaluate ours. Brake caliper frozen. Both need replaced. $475. I stated go do it. They ordered parts, got us a $20 rental car so we could run back home for the night, as we were on 20 miles from home.
It was done the next day by noon. It still pulled until the new pads broke in, but got better the further we went, the better it got.
That unit has been sold.... Replaced with a new Chevy 4500 Sunseeker. We are anxious to get on the road with it.