I want to jump in on this discussion as i’m Having a similar issue with my 2011 model. Mower ran great for about 7-8 years with no major problems and all of a sudden I start getting grinding noises like cruise42. Replaced plastic gears once and everything was good for awhile,but grinding returned and slowly destroyed the plastic gears. I had seen on YouTube were you could replace the plastic gears with metal ones and I did this upgrade to the tune of about $60 U.S. All good once again,but lately been clicking and today got a grinding sound at one point,usually happens when the bag has some clippings in it thus extra weight. I’m starting to suspect that maybe the transmission gears are getting worn and causing it to slip under load. Can these transmissions be rebuilt or is it easier just to replace them ?