Im in my mid 60s and had met my daughter and grandchildren at the mall. It was dark.When I started the engine to come home,it would not go into reverse gear and their was a horrible grinding noise. I was parked on a slight hill and the vehicle rolled backward so I was in the pathway of other vehicles. I was pushed out of the way. I continued to try to get it to go into a gear to no avail. I called AAA and sat there with the motor off until they arrived.When they arrived,the envoy started and drove as if nothing had happened. I figured that it was just a freakish one time happening so I forgot about it. Well, my husband and I went to lunch on Saturday05/10/08 and it happened again. I called AAA and as I was giving directions, I decided to start the envoy. You guessed it, it started up right away and again,drove as if everything was perfect Can anyone please help. I now feel very unsafe with this vehicle.