My Ranger Hard shifts?

I have a 1999 Ford Ranger V6 Automatic. up until not too long ago it ran just fine. then one day the truck decides to hard shift most of the time it changes gears. also at the same time the engine started stalling from a stand still when a little bit of throttle is applied. and once it shuts off and i turn it back on it doesnt stall for a while but the shifts are still hard. i got it checked and they told me it had a misfire in cyl 4. idk what the problem is