MrChubs1

I've installed Richmond 3.90s in a GM 10-bolt before and they were silent.

I recently got 3.90s put in my Mustang and they whined a little on decel only (just like you're describing). The whine was so minimal that I figured things would only get worse if I brought it back to get it corrected. I figured I'd end up with no decel whine, but cruise and accel whine, so I left things alone. Now, about 700 miles later I think the whine has reduced. I'll have to really pay attention to see next time I drive it.

All that said, I totally agree that 95% of gear whine is due to poor setup. It really depends on how loud it is. If we're talking about something very slight, it's probably not worth the hassle of messing with it.

DesertMach

I have the Motive gears, and I never had any whine after the install.