Hey Scotty, I have a 98 mustang 3.8 automatic. Recently my O/D off light has started blinking when I drive my car. The light will not come on if I have the car in 1st or 2nd gear, it comes on when I put the car into drive. Also when going up a hill at a slow speed the car will start shaking a little and I have to press the gas more to get the car to downshift to get up the hill without the car hesitating. Also when I’m in drive and I slow down to a stop the car downshifts roughly with a slight jerk. Any ideas on what this could be? Maybe speed sensor?

you need a pro like me to scan it with his dealer level scan tool to access the tranny trouble code that has set. No way past that, start there, then post the code here