2000 Dodge Intrepid Speedo at Zero, 4-5 RPM travelling in i

Was entering into Interstate, suddenly realise that my speedometer remains at 0 while my RPM increases when i accelerates. After that, i turn off my car and restart, the engine check light on and when i accelerates, there is jerk (as if switching from 1st gear to 2nd gear). Throughout the jounrey, the RPM increases to 3-4, Speedo remains at 0; travelling in appromixately 50 MPH. Many comments mentioned that is the transmission at fault. Is it true? What is the possible solution for the problem..