Transmission Whine in Reverse
 

I got a 08' xB 84000 miles...just started having a whining sound when going in reverse. If I stop the whining stops also. Any thoughts on what it could be.

Too me it sounds like if you let the air out of a ballon while stretching the open end.

this is normal.
It's the gear itself clicking.

reverse is a straight cut gears

and this is what straight cut gears sound like