Allis Chalmers 170

I have a problem (like you haven't heard that before) I used the tractor this weekend for spreading some dirt around my yard with my 3pt blade. I only spent about 30 minutes or so spreading the loose dirt around to fill in low spots in my yard and then parked the tractor. Everything operated as it should with no noticed problems. The next day I went out to spread more dirt, and when I went to back up the tractor only the right wheel would move in reverse. The left wheel acted like it was locked up so I shifted into 1st and the tractor moved forward like normal. I then tried to shift into reverse again and the same thing happened with the left rear tire not moving. Next, I jacked the tractor up in the air and shifted into neutral and it was easy to spin both wheels in both directions. I then shifted in reverse and spun the wheels, and the opposite wheel spun in the opposite direction (I did this on both wheels). I repeated this with the trans shifted into first and they both spun in the opposite direction (I did this on both wheels) as well. I then lowered the tractor, started it and shifted into reverse and the left wheel was still locked while the right one tried to spin. As per the above when I shifted into 1st the tractor moved forward fine. Any help would be appreciated.
Semper Fi

Sounds like the left brake has ate her pigs. You can remove the dust cover from the top of both brakes and take a look down inside with the seat in the up position. I'll bet there's a broken spring or the disc lining is worn too thin. Axle and wheel have to be pulled to work on those brakes.

Thank you so much. I'm new to working on tractors and greatly appreciate your advise!