Welcome Jim! 
My first thought would be a safety switch causing it to stall since pressing the brake will keep it running. Namely the seat switch or something in that circuit. When it stalls does it act the same as turning off the switch or does the engine act like it is under a very heavy load?
On my LT150 as I recall without pulling the bypass rod it will move one direction if you push hard enough but will lock the wheels going the other direction. Of course when you pull the bypass rod and it moves easy both ways.
My first thought would be a safety switch causing it to stall since pressing the brake will keep it running. Namely the seat switch or something in that circuit. When it stalls does it act the same as turning off the switch or does the engine act like it is under a very heavy load?
On my LT150 as I recall without pulling the bypass rod it will move one direction if you push hard enough but will lock the wheels going the other direction. Of course when you pull the bypass rod and it moves easy both ways.