I have a Troybilt (Super Bronco) riding mower model 13AZ60TG766. At the end of this mowing season 2014, I was mowing and gradually the mower moved slower and slower and now will now not move if your going up a slight incline. I had recently replaced the ball bearings, greased the transmission, and replaced the front and rear drive belts at the same time. I also replaced one of the Pedal springs. When I started it back up everything worked great. It was only about an hour and half into mowing when the mower started slowing down. I noticed if I pumped the front pedal then I could get the belts to catch and move the mower forward, I can push the pedal all the way to the floor and it simply won't go any faster, and I can't push the pedal any harder. This is a variable drive mower, with just forward/neutral/reverse and the speed comes from how far you push the drive pedal. I've looked underneath the mower and the pedal seems to be doing what it's supposed to do - tightening the whole drive belt system so that power transfers from the engine pulley to the transmission pulley in the back. Any suggestions?