Why do cars (transmissions I assume) sound different when they are backing up than they do when they are going forward?

Question

In reverse they tend to make a whining noise. Isn’t it the same parts doing basically the same thing either way?

In: Engineering

Answer 1

Most of your forward gears are what’s called helical cut, so if you look at it from the side the teeth are sort of diagonal. Your reverse gear is usually straight cut, so if you look from the side the teeth look to be all straight. Helical cut gears are more complicated to make, so they’re more expensive, but they’re worth it because they’re quieter. But since you’re rarely reversing for that long, they cheap out a little bit since the noise doesn’t matter there.