Lawnmower will go in reverse but not forward it's a hydrostat troybuilt what would cause this?

SOURCE: FORWARD AND REVERSE GEAR SELECTION BACKWARD

Recheck your belts, does your engine have a pto

SOURCE: MTD 42 inch hydrostatic drive lawnmower

1...first and foremost check the fluid level and top off with mobil 1 full synthetic 20w50 oil,
2...check the the engine pulley for wear
3...check idler arm spring tention.
inside yout transmission is a center pump section and swash plates and a set of 6-8 pistons , if dirt is allowed into the transmission it causes severe wear to these parts

my recomendation would be to dissasemble the transmission and inspect the pump center section and swash plates for wear....look for tiny scratches on the bearing surfaces, if it is worn then replace parts as needed. these worn parts will cause the transmission to "growl" or as you say "grind"

SOURCE: lt1000 hydrostatic drive stuck - will not engauge or disengauge

Does the tractor try to move or **** in any direction, if so you may want to check to see if the disk that controls the brakes is stuck, I've seen this many times.

SOURCE: my 4210 4x4 with hydrostatic

Hi, the engine will power the hydrostatic drive via a drive belt. See that this belt is in place or if it is worn out and loose. By replacing this belt you should get your machine running again. Hope this helps

SOURCE: The transmission is slipping on

http://cubcadet.custhelp.com/app/answers/detail/a_id/1722/~/cub-cadet-technical-service-manuals