Well, looks like this has been getting messed up for a minute or two.
I put the tractor up on ramps and looked at it. Found the belt partially shredded, so I tried pulling on it.
My granddaughter helped me push it to the shed, and when we moved it the impeller was laying on the ground.
Looks like the belt came off the pulley, rode on the impeller, partially melted it and shredded it all at the same time.
This may be more fun than I thought it would be.
I have the service manual, but don't know which direction to go here.
Please tell me I don't need to pull the transaxle to replace the impeller (if it's even a replaceable part).