1993 Ford F-150 XLT

I drive a 1993 ford f-150 with a four speed automatic. It has the 5.0 v-8 I have not had any mechanical problems at all with this truck. I obtained the truck from an elderly gentleman who did not drive it very much. The truck only has 82000 miles on it. This past week I was driving around town and when I took off from a stop light the truck shifted really hard and allmost threw me on the floor board. Since then I have noticed hard shifting at low speeds and somtimes when taking off from a dead stop it shifts so hard that it seems like the transmission is going to fall out. This truck is an everyday driver and it has been taken care of. What is causing the shifting problem? I have a friend who told me that every 1993 ford f-150 needs to have the transmission rebuilt at around 80000 miles is this true?