580C Left Rear Wheel Locking Up (don't think its brake issue)

I am new to this forum but have read quite a bit on it and it's helped me a lot in the last few months. I have a 580C that I bought about 8 months ago and got a smoking deal (at least in my mind). Since then I removed and cleaned up the brakes, replaced seals, master and slave cylinders. I also rebuilt all of the hydraulic cylinders.

I was moving snow last week and the left rear wheel locked up on me. I had to use the hoe to move it out of the way and haven't been able to move it since. I have read a lot about it being the brakes locking up but I'm not sure that is the case here. If I raise the rear of the machine with the outriggers, both wheels turn freely under power from the machine. The wheel only locks when on the ground. This leads me to believe its a bearing or something on the rear end. Wouldn't the brakes lock either way? Has anyone experienced something similar to this? I am hoping to dig into it this weekend and would like some direction instead of flying blind and disassembling everything. Thanks in advance for any and all help.

Could still be a brake issue, machine has enough torque to turn the wheels when off the ground even if brakes are tight..Can you spin the l/s wheel by hand? Does it make any "clunking" noises when turned back and forth? Try spinning tires while off the ground with the machine, (don't go crazy or something may break, just a disclaimer) then feel the l/s brake housing to see if it's getting hot..If so back off the adjuster on top of the housing, You'll have to move the adjuster lock "lever" away from starwheel before backing off brakes, see if that does anything..Also make sure the brake levers on top of the housings are well lubed and move freely,andif you've used the E-brake lever, make sure that's not sticking...

How does your brake pedal feel? Have you tried backing the brake adjuster off and see if that takes care of the problem? Do you have any side to side or up and down movement in the rear wheel? Take rear wheel off and check play in axle.

Ok so I finally ad some time to mess with it last night. I backed the brake adjuster nut off a couple turns and also checked for wheel play. The axle seems to move in and out maybe a 1/4". No up/down or side to side play. I tried driving it after this and it drove fine around my driveway. Its too muddy to go anywhere else with it. Now my question is how would the brakes adjust themselves tighter? I don't have the locking pawl for the brake adjuster. I adjusted them late last summer and used it all winter to clear snow and move things around on the property. There was no warning to the issue, just locked up all of a sudden. My assumption is that the brakes would actually back themselves off without the locking pawl giving me weaker brakes not better.

One possibility is that a piece of band / lining material broke off and jammed it.

It’s possible that the expansion balls got out of place and wouldn’t let drum return to normal.
Do you have a lock nut as adjuster or are you using a jam nut?

You may not want to hear this.... Pull the brake cover. If something there falls out... you know what you have to do. If everything is good in the brake.... it is the rear. If its the brake and you get it released you can get back into a warm dry shop.

If it is the rear and something is broken you don't want to make it worse.