Re: toro self propelled mower
I had the same issue with my mower earlier this year (not a Toro).
Stop and think... there's some mechanism that transfers engine power to the drive wheels. Usually that's a belt under the mower deck with some type of cover over it to protect it. There's usually a hand lever you squeeze to engage the self-propel drive - that lever pulls a cable. At the other end of that cable is usually an idler pulley that tightens the drive belt around the drive shaft and transfers that power to a small transmission that poers the drive wheels.
Belts do stretch, and the inner surface can get glazed from slight friction over the years.
All that said...
1) If you don't have the owners' manual, get one. If your dad doesn't have the manaul, you should be able to find one online, or at worst, buy one from a Toro dealer. The manual should give you specific instructions on how to do this.
2) Set the mower up on blocks or something. DISCONNECT THE SPARK PLUG WIRE! Take off the mower blade and clean everything you can.
3) Remove the belt guard(s) and clean everything you can.
4) Take some digital photos so you know for sure how everything was routed for when you go to reassemble.
5) Remove the drive belt and replace it. Clean everything you possible can.
6) Check the cable tension and idler pulley to make sure it engages. You may need to replace some springs. BTW - cables stretch, too. There's usually an wheel to adjust cable tension, or if it's all the way, you may need to replace the cable.
7) Reassemble. Be absolutely positive everything is back the way it was. Test the levers etc. It should work.
8) If it doesn't work, then further diagnosis is necessary. Possibilities at this point:
a) failed transmission (from the drive belt to drive shaft)
b) failed cogs within the drive wheels. As the drive shaft turns, there's usually a cog / lever that turns and presses against star-like teeth connected to the actual wheel. Again, photo, clean, re-grease, and reassemble. If you see something loose or broken, replace it.
HTH
Al