I was driving and I heard a whining sound in my automatic transmission (2 wheel drive vehicle) the whining sound stopped. I could continue to drive forward but noticed that the engine would Rev to about 3500rpm before it shifted into second. I stopped to park and my blazer would not go into reverse. presently, I can go forward but not in reverse. My blazer is parked in my garage. The fluid level is within range. Can anyone tell me what is wrong and what needs to be done to fix the transmission?