1979 550 John Deere steering problems

I have a 1979 John Deere 550. The problem that I have with it is when I try to turn to the left in forward or reverse it stops moving, I then have to put it in neutral and back in either forward or reverse to get it to move. It works fine steering to the right. It seems like when I try to turn left that the clutch on the right stops pulling, but not all of the time. Any ideas on what might be going on with it. Thanks...

1979 550 John Deere steering problems