the rpm's do not go up, seem to stay put. brakes remain hard, feels like I'm pushing down as hard as I possible can, and almost like my foot is slipping off the pedal because brake is so hard. This also happend once while backing out of a parking spot, I was in reverse, with foot on brake and my car just started rolling backward. The mechanic who looked at it yesterday said the brakes seemed responsive but wondered if maybe this could be a transmission issue? What do you think? Thank you so much.