My first thought was TCC solenoid shot, but you said you replaced it. If you unplug the harness from the driver side of the trans does it still misbehave? Might be that your TV cable isn't adjusted correctly, but others might be able to speak to that better than I can.
~ Matt H.
1988 Monte Carlo SS w/ T-tops, White with gray int, 350, Summit cam, World Torquer S/R heads, Holley St. Dominator intake, Edelbrock 600cfm carb, Champion 3-row alum radiator, ramchargers, 200-r4 with CK Shift Kit, billet servo, 2200 stall, Afterburner headers, Pypes 2.5" with x-pipe, Violator mufflers (stock exit), S10 front brake swap.