Small Engines (Lawn Mowers, etc.): Toro 20017 Grinding Noise when Self Propel is Engaged, rear wheels, rear wheel drive

Question
I just recently replaced a drive belt on my Toro 20017 push mower (rear wheel drive). Everything worked fine for about 30 minutes, then a grinding noise appeared in the self propel. I can pick the rear wheels up when the self propel is engaged, and the noise stops. As soon as the wheels hit the ground and the mower starts moving, the noise returns. It is especially loud when making a turn. Any suggestions? Thanks

Answer
I think the gear inside the rear wheels are worn.  Take the rear wheels off and inspect the gears.  You cannot replace it you have to replace the entire wheel.  Do not heavily grease this self propel system.  A lot of  grease attracts a lot of dirt in dirt will grind away the gears.  I hope this helps