Dragging rear brakes on one side

[MikeB]

After 50 miles or so of driving and stopping, especially from higher speeds, the left rear shoes on my 82 C10 start dragging. When I let off the gas to slow down, the brakes seem to lightly pulse – “grab, release, grab, release” with each revolution. Acts like a high spot on the shoes and a high spot on the drum are lining up once per revolution. I know it’s the left rear because the wheel center on that side is 40-50 degrees hotter than the right side.


However, when I get the truck up on jack stands the wheel spins freely. And if I drive the truck a few hours later, there is only a slight hint of the problem. Drums shoes, and wheel cylinders have less than 2K mile miles on them. Shoes fit the drum curvature perfectly. Rear hose is new, and the right rear is fine. I don’t know if axle bearings have ever been changed, but there is no seal leak. Pulling the drum shows nothing strange. If I back off the adjustment, the problem goes away for a while, but self-adjustment brings the shoes closer to the drum and the problem returns. I’m wondering if the brake drum is going out of round when hot. I'm very close to replacing drum, shoes, wheel cylinder and axle bearing on that side.

Any suggestions?