Is it possible for tire noise (flutter) to be worse on decel (coast) than accel (tip-in)?

I've had my ring & pinion "fixed" 4 times, one of which was a whole new differential. They've all had varying levels of whine. This latest is more of a flutter, like a pigeon in my trunk, from about 60 mph tp 30 mph. Loudest at 45-50 mph. I hear it slightly at all times in that speed range, but it definitely gets louder about 1/2 sec after a take my foot off the gas. My dealer s trying to tell me it's normal tire noise and not the gears. I'm skeptical because it's louder on decel.

 

I'm on my 4th set and they whine like a baby. Now I am out of warranty Does the warranty extend beyond 36k if the gears were replaced at 20kmi? The guy that tried to fix them last time said he reduced the spacing to the low end of normal gapping and this is worse than the original whine I had.