I've only had a few of the 2 rear wheel drive Toro mowers but they look the same as the AWD except no front self drive axle.
I probably just check the drives the same as you Norm ,spin the pulley make sure the axles turn then remove the wheels and check the drive gears ,the drive type is common with the drive key having a flat on the drive side and a taper on the freewheel side , then making sure the parts are installed correctly and not excessively worn. The drive key shouldn't be stuck in the axle slot it should move freely.
When I get Toro mowers I throw them out after taking parts off, so I may still have working self drives if you need free parts.
