Anyone had this problem before, when you go to revers the stereo volume decreases, when taken from reverse to drive or park it goes back to normal.

I find that kind of funny... I never noticed it in my car. It would seem the speed compensated volume should only work in forward, have you tried turning it on/off?

right - it's the speed sensitive volume.

Well, I would either stop going in reverse....or turn the radio off when i do.....lol :D

you have the rear parking sensors? mine quiets down in reverse and I assume it's so you can hear the beep-beep-beep before you run something over.

Same here. Mine only lowers the volume when the reverse sensors are going off.