Gear set for gear motors (ET, M20 and M24).
When the gear set inside the motor is damaged, it needs to be replaced. Gear set and gear parts that need to be replaced due to wear. Check them once every 2-4 months.
If the AT board (ET, M20, M24) motor have a different big sharp noise, it needs to be greased (High grade trailer bearing, lithium marine grease.). Or need to replace the gear parts.