Whenever I push on the gas pedal while in reverse, my 1999 Suburban begins to make a buzzing sound of some sort. It's not overly loud, and hasn't seemed to affect my transmission or ride quality, but its only been going on for a few months and I'd rather not have it get worse. Not sure what could be the cause of it, but the transmission did get used pretty hard during the past winter when we had over 2 feet of snow for a few weeks (did a lot of driving back and forth quickly to plow through).