Clicking/crunching noise from rear wheel on a RWD mower

[Scipe]

Hi,

I have a Lawn boy I got at home depot about 3 years ago:
https://www.homedepot.com/p/Lawn-Bo...Lawn-Mower-with-Kohler-Engine-17732/204635396


So I started to hear a loud noise from the rear wheels of the RWD Lawnboy. I took the wheel apart but didn't see anything stuck or broken. I got to a small white plastic enclosure (transfer case?) where the arm that drives both wheels goes to. Any idea how to repair or what may be the issue?

 

[Rivets]

Take a close look at the plastic gear on the drive wheels. Willing to bet it has teeth which are worn away. Will need to replace the drive wheels. Before doing so take an even closer look at the bearing hoc, where the axle goes through. It may be worn, which will cause the gear wear and tear up new wheels if not corrected.