reverse whirr.

All to do with the shape of the teeth on the gears in the gearbox, I'm told.

Cheers Gary

it may be that reverse gears are stright cut whereas forward gears are bevel which are quiter. could also be that the diffs etc are moe worn in running foreward. dunno. perhaps an engineer will know Richard

high-pitched

Yeah - reverse uses straight cut, or spur gears, whereas forward gears use helical gears. Helical teeth are cut at an angle across the face of the gear, meaning that they make contact in a more progressive way. This gives less vibration, less wear, and smoother engagement, but with greater sliding and therefore more need for lubrication.

Since most of a vehicle's time is spent going forward, and since reversing is usually done at lower speed, it makes sense for cheaper-to- produce spur gears to be used in place of the more expensive helical gears for reversing.

Here's a handy link if you want to know more :

Having now read the link in your message, I think my previous reply was probably total bollocks.

DaveP

thanks guys. that will satisfy my curiosity for a few hours till i find something else i don't know about. for a while i thought it may have been a deliberate safety thing like trucks beeping when they reverse. but obviously not.

thanks.