early TCC engagement is a computer control issue....why I do not know. However, with my 3.8 and 4 speed 4T60, TCC indeed engages rather soon after 3rd , then shft to 4th is done with the TCC already ON...I think the computer control eases the power for a fraction of a second to make it smooth...but this is speculation, not actually tested .
About late release, it would be interesting to monitor the signal to TCC solenoid, live,--this is a separate plug with this signal only- just to see if actual release occurs at signal off...or if it occurs after that...which would indicate tendency to sticking.
www.avigex.ca/xport/3T40tccplug.jpg
http://www.automotiveforums.com/vbul...d.php?t=551757