1995 Nissan Altima; 113,100 miles; Automatic - While driving, my car would intermittenly fail to move while the engine accelerated. It would only happen occassionally and I didn't pay too much attention to it. This started about a week ago. In the past 2 days however it really started acting up and began not moving at all sometimes when in reverse. I finally got smart and checked the tranny fluid and found that it was extremely low. I filled it up and now the car always moves in drive, but struggles a lot to accelerate and it still won't move in reverse. What kind of damage did I do by driving it with such low fluid and what is the average cost of repair for the problem? I appreciate any guidance you can provide me before I go and get a mechanic to look at it.