I have a yardman[mtd] riding tractor but when I put it in forward it will not move,but it will move into rev. Took rear end apart and all gears look fine. Have now idea what problem is??

Hi,
It is generally the adjustment of the shifter linkage; located on the left side of the machine usually and is a 1/4" bolt requiring a 7/16" wrench or socket to loosen and adjust int a "true" neutral.
Peace,
Clarke