ego self propelled mower making a grinding noise from the wheels, what's wrong?

You've likely got debris packed into the self-propelled gear set, or a gear is worn.

1. First, tip the mower on its side (discharge chute away from you) and clear any packed grass or twigs from the wheel area.
2. Check the gear set (part number 2826428002) inside the self-propelled unit for visible damage or missing teeth.
3. Listen to the motor & gear assembly (part number 2826577002). A grinding noise from there means the unit needs replacement.

If that didn't work, inspect the wheel assemblies (part numbers 2825267001 and 2824429003). A bad bearing in the hub will cause grinding. Spin each wheel by hand to check.

Heads up: Regularly clean the underside after mowing, especially in damp grass, to prevent debris buildup.