gear box whine in reverse(automatic)

[old cruiser]

Had to reverse up fairly quick today at one point today and noticed the gearbox (mine's an Automatic) whining slightly, bit like I used to get in my last car which was a civic manual transmission, understood the reason for that due to straight cut gears for reverse, but didn't think that was the case for the automatic transmission, can anyone enlighten me and tell me if it's normal to hear this?
Cheers Pete

 

[GSD2013]

I had a similar issue with my old merc W123 type, turned out to be low transmission fluid and worn engine mounts, the rubber ones. The auto box would take time to shift, and become more jarring, or jerky with changes, the whining sound was the engine vibrating when shifting into reverse.
Is your ATF fluid in service period?

 

[old cruiser]

It is mate was only changed a few months ago, have since heard that the reverse gear does in fact have some straight cut gears like in manual cars , which explains the noise , if I reverse slowly as I normally would don't hear anything, only if reversing at a fair speed.
Cheers Pete