07 volvo 780 driver's side rear drives locked up

On this '07 volvo 780, the driver's side rear drives are locked up. All other wheels turn normally including the wheels on the passenger end of the same axle. Brake chamber push rods extend and retract and brake cam shaft rotates normally. It's almost as if the brake shoes are frozen to the drums. It is well above zero here, so it's not ice.

This happened suddenly (while truck was parked, thankfully) with no previous warning signs like noise or jerking or noticeable excessive heat or anything else at all. Working fine, turn it off, start it up after being parked for a few days, wheels locked. Just like that.

RT40-145/3.730 Arvin Meritor Axle and brakes, Bendix ABS, has TCS (traction control system). No diff lock in this axle.

It seems like this ought to be something simple that I've done wrong and I'd appreciate any pointers before I take apart more than I have to.

Thanks in advance.

 

For some reason, the thanks button doesn't seem to work for me but anyway, thanks to both of you.

First thing, I'll figure out whether it is brake shoes jammed or seized or something internal and go from there. It shouldn't be a big problem as long as it's not something electronic.

Thanks again.

 

Not yet. I will post here when I get it fixed. I'm kinda leaning towards the idea that it's likely an ABS fault. I'm no stranger to a wrench but I don't know much about this machinery, and even less about the electronics, so we will see. Wish me luck.

 

Pushrod does move and retract normally. I will check again to be certain. Thanks for your comment.

 

Will try that. Thanks for your comment.