Why does my manual transmission car make a loud whirring noise in reverse?
Why does my manual transmission car make a loud whirring noise in reverse? Manual transmissions use mostly helical gears , but reverse is a special situation that requires a different type of gear – a spur gear . The gears that make up the forward gear ratios are all helical gears. The teeth on helical gears are cut at an angle to the face of the gear. When two teeth on a helical gear system engage, the contact starts at one end of the tooth and gradually spreads as the gears rotate, until the two teeth are in full engagement. This gradual engagement makes helical gears operate much more smoothly and quietly than spur gears. Also, because of the angle of the gear teeth, more teeth are in engagement at any one time. This spreads the load out more and reduces stresses. The only problem with helical gears is that it is hard to slide them in and out of engagement with each other. On a manual transmission the forwar
