rear wheel lock up

[c30bob]

Hello! After a long winter I decided to finally start playing with a project I bought last fall, a 1974 c30 dually. The right rear wheel locks up with just forward motion, with out touching the brakes. Jacked up, with the wheel in the air, it spins free. I unhooked the brake line from that wheel cylinder and plugged the line. Still, forward motion, without touching the pedal, the wheel locks up. I backed off the parking brake, same deal. I'm thinking it's a mechanical issue with the parking brake internals in that drum, but I'd love some wisdom before I tear into it! Thanks

 

[nabeshin]

Take off both drums to compare the two assemblies.

With the wheels up, does the axle turn smooth or is it rough and crunchy? Does the wheel lock up instantly as you start to move? When it does lock up, does going in reverse release it?

 

[c30bob]

In the air it spins free and smooth. It's almost always instantly locks when moving forward. Reverse does indeed release it. Haven't had it apart yet to compare, but hopefully I'll get it in the garage soon. Thanks

 

[nabeshin]

I had an issue with the right side rear brakes dragging when doing down the road (temp gun sensed a 100+ degree differential between sides), but it would spin free when up on jack stands. Little noise when spun free. This was after I replaced both rear shoes, wheel cylinders, and springs, etc.

Turns out, the axle bearing had worn down the axle shaft. The whole axle shaft was able to be jiggled up and down. With the weight on it, the axle essentially rose up in the housing, enough to drag the bottom of the shoes.

Check for play in the axle shaft, up and down with the drums off. Mine was pretty pronounced. If it was more, then maybe that is enough to drag and stop?

 

[c30bob]

No real play in the axle. Only moves inches before locking up, without touching brake pedal. Brake line removed and plugged on that side, parking brake is backed off. Feels like just forward inertia is setting it off.....

 

[nabeshin]

No real play in the axle. Only moves inches before locking up, without touching brake pedal. Brake line removed and plugged on that side, parking brake is backed off. Feels like just forward inertia is setting it off.....

Did you ever get the drums off to look about?