I have a yard machines lawn tractor. The mower starts, the blades engage. But the tractor will not move forward or in reverse. My father said some tractors come with a transmission disengage switch for transporting.. Does such a switch exist? And if so where is it?

SOURCE: mower stopped dead. blades go, tractor starts and

broken drive belt

SOURCE: I have a craftsman lawn

If you haven't done so check drive belt to make sure it is fully engaging when you put it in gear. You can also check to make sure that your break is fully releasing.Grasp pedal with your hand and pull it back to make sure it is returning. Thank you.

SOURCE: craftsman lawn tractor automatic transmission

Just like motor vehicles when transmission gets stuck on a particular place without moving forward or backward it is a sign of a jam in one of the transmission levers. This is usually caused by lack of transmission fluid in the gears.When the fluid or grease depending on what your unit uses gets low the levers begin to grind against one another and therefore bring about such problems as you are facing. Although there is an off chance that the problem could also be from the automatic selector in this case the damage might not be so much probably an electrical fault.
First get an expert to check the auto selector if it is in good shape. If it is then i am afraid the problem is from the transmission levers.
Hope this insight has been helpful?