Just bought high mileage car, drove 1000 miles last 2 days for delivery. Seemed to drive fine, just drove a couple of miles this afternoon and tramsmission troubles developed within 1 mile. Car shifted back and forth between third and fourth rapidly and then nothing. No gears work. Sensors on transmission or is the transmission gone? Also I could push the car not running forward in neutral but could not push it backwards. Anybody got any ideas how bad the news is ?