The "whir" in reverse for most vehicles is caused by the reverse gear having different types of teeth than the forward gears. These gears (spur instead of the normal helical) are much easier to get into place, but distribute the stress less evenly, causing more noise and wear. Since most vehicles don't back up a lot, this is an acceptable trade-off.
According to https://en.wikipedia.org/wiki/Grumman_LLV the LLV has a THM180 (3-speed automatic --- one of the lightest duty ones in the range, so a bit surprising to find it used here, but then again the engine isn't all that powerful either) which has a compound helical-cut planetary set, so it wouldn't have the characteristic straight-cut whine and only in reverse.
Do the other cars on this list have the same reverse sound?
I suspect, as another commenter here remarks, that it's mostly due to a lack of noise dampening.
Also, straight-cut gears are better at basically everything except noise, which is why large truck transmissions, racing, and off-road heavy equipment still use them. They have no side-thrust unlike helicals, and can take far more torque; the only disadvantage is the noise (which some car fans admittedly like --- including me. :-)
> straight-cut gears are better at basically everything except noise
Noise means vibrations. Which is why e.g. cheap lathes and similar machines have cheaper spur gears, while high end machines often have helical gears. This impacts surface finish, for example.
Makes sense! I've definitely heard similar "whir" on many (most?) vehicles when reversing, but not quite the same as the incredibly distinctive sound an LLV makes. It's really an identifiable & unique sound on them specifically, probably just a certain gear/mechanical that's use for LLVs I figure.
Funny what sticks out so bluntly in one's memory, though! :)
Sounds tend to anchor pretty strongly in people’s memory, I think only smells have a tighter bond.
The cut of the gears could be a factor here, but the (lack) of sound insulation could be it too. Cars have aimed for a “refined” feel for decades, with minimization of unwanted noise being part of that. There are many words one could use to describe the LLV, but “refined” probably isn’t one of them.
