dryer drum doesn't turn when pushing start button

I have a maytag dryer that i am having trouble with. The first problem that started the whole thing was a loud squeaking noise. I have replaced the rollers, dryer belt, tumbler bearings, blower wheel, and the Motor. Now, when the drum will not turn after pressing the push to start button, but if i push the button and turn the drum by hand it will run. Could this be a bad switch to start the motor? this was happening even with the old motor before i replaced it!!