Tractor Repair: Allis Chalmers CA, allis chalmers, rear wheels

Question
My tractor start and runs great. However, it will not move when engaged recently. I make a "slap" sound in the rear tire axle area. Sometimes, it will stop moving after the front blade hit a pile of dirt or snow, then shift into reverse then the slap sound. I usually turn it off and come in a hour then it will go into reverse. Thanks for any help.

Answer
 If it sounds like it's in the rear axle area, then obviously it's not a clutch problem.  It's either a differential or final drive problem.  When it won't move, try applying each brake one at a time and see if that will make it move.  If so, the differential could have failed, or one of the final drives has an internal problem.  The differential will supply power to whichever side turns the easiest, so if one side is not driving the wheel because of a failure, that side will turn and not the other so the tractor won't move.  By stopping the side that is turning with the brake, it may supply power to the other wheel and make it move.  But it is possible for the differential to fail in such a way that the brakes won't help either.  I would suggest jacking up the rear wheels off the ground and turning them by hand.  Listen for noises and you might be able to find out which side has the problem.