toyotaoffroad91

hey guys i have a 91 pickup. i have an itermittent problem. my torque converter will some times lock up at very slow speeds ( under 10) it causes my rpms to drop drasticly. i have to floor it to get it unlocked and then it feels like it slips a little and then lock up again its almost like a bucking sensation with an occasoinal shutter. i have also noticed when just coasing in drive i hear a clicking noise coming from the bellhousing?? bad converter?? i replaced the lockup solenoid but maybe theres dirt in there. also replaced TPS, nuetral start, coolant temp, speed sensors, any ever have this problem