Transmission slipping....or something else

OK, I have a friend with a 2002 F-350 automatic 89,000 miles. When taking off from a stop sign or red light you give it gas and it jerks every time. RMP's go up and then it just jerks when it takes off. Stealership said that these trucks just do that. They said that they greased something and friend said it worked fine for a while. Anyone have this problem before? It shifts through every other gear just fine. Thanks