You can replace the TCC solenoid and see what happens. I have see these fail but I have also seen internal transmission problems cause this, usually after a rebuild where a seal or clip was installed incorrectly. You could aslo try servicing the transmission with a new filter and new fluid. You might want to take it to a transmission specialist. They will run into these types of problems more often than repair shops.
Could you give me the year, make and model? I will locate the TCC solenoid for you.
On your transmission it is under the side cover. I would have a transmission shop look into it and let them run some tests.
The steps look pretty easy but they might assume the transmission is already out. Usually having enough space to work is the problem. Here are the steps anyway:
Remove the case side cover. Disconnect the Torque Converter Clutch (TCC) solenoid electrical connector.
Remove the TCC solenoid retaining clip (314) Remove the TCC solenoid (315).