2001 Chevy Venture torque converter slipage

when we go on long trips it will slip and shift hard. my check engine light comes on and reads (torque converter clutch slipage) which reads that either a stoped up line or tcc soleniod bad. i was told to change tcc solenoid and pressure switch when i do a trans serviceand if that dont work then torque converter is bad. just need some extra input .thanks