slipping

First blade replacement. Went very smooth. Maybe too smooth. Completed the installation, took the mower out for a test-drive, it was working great. About 5min the blades stopped turning. Disengaged the blades with the cutoff switch, took it back into the garage, lifted it and checked the torque...

Just replaced pinion gears, and adjusted the drive engagement: Under no load the rear wheels full engage and drive properly, but in use if I "fully" engage the paddles, the gears "chatter" and seem to skip. (Note: the old pinion gears were substantially worn done nearly 75% of the way, with only...