Hey everyone.

I have an 08 Accord LX-P auto and it makes this cool whining sound. Is this normal? It's really loud when I back up fast. I don't know how to describe it but it sounds cool to me though. Does anyone know what I'm talking about.

 

Umm yeah....that's normal.

 

yeah, mine makes that sound too.
I think there are lots of other cars that make that sound when they reverse...?

 

With manual gearboxes fitted to road cars, the teeth on all the forwardgears are angled because angled gear teeth operate very quietly. The teeth on the reverse gears are 'straight cut' (i.e. not angled) and straight cut gears areinherantly very noisy.

The reverse gears need to be straight cut because they are not in'constant mesh' (as all the forward gears are) and when reverse is selected or deseslected it's the gear teeth themselves that move in or out of mesh, and this is only possible with straight cut teeth (with the forward gears the gear teeth are always in mesh in all the gears all the time, the gears being selected and deselcted by means of 'dog gears' that slide on the main shaft, so quieter angled teeth are possible).

Many racing gearboxes use straight cut gears on the forward gears as well because straight cut gear teeth are stronger than angled gear teeth, and because angledteeth create 'side thrusts' inside the gearbox as the angled teeth try to slide laterally out of mesh with each other (which they can't do, butthis does create additional friction, moreheat, and less power to the wheels). This is why many racing gearboxes make a loud shrieking noise, often as loud as the engine, and sometimes louder.

 

You shouldn't be hearing it when the car moves forward.