After 10 years of use the liftmaster garage door opener failed humming inside but making no movements outside. After the technician arrived and inspected the problem, he found the nylon gear inside had striped out. Replacing the liftmaster nylon gear, the garage door opener started to engage again and pulled the traveller up and down. The reason of the nylon gear stripping out was because of the tension spring ontop of the garage door had lost its tension. When a tension spring starts to lose tension, it means its ready to brake. The way of finding this out is by disengaging the motor and running the garage door manually. If the garage door stays at any height you put it to and doesnt fall immediately this means the tension spring is ok. After replacing the tensiom spring the garage door operated properly and the garage door motor had no issue opening and closing.