Me and my dad changed the drive belts on my 1999 troybilt with a automatic trany and at first the shifter will not go in to gear the shifter will get stuck and will not move to the forward position after being in reverse but now since we fixed that problem the tractor will not go fast like it used to it goes so slow when pushed on the pedel we tried adjesting it but did not work and pedal hard to push sometimes. What's making it go so slow? Please help!!

Sounds like belts are to long or on the idler pulleys wrong .