4L60E trans parameters

[Detroit Gearbox]

You might just try replacing the tcc solenoid (internal harness) and inspecting the tcc valve (above the tcc solenoid) sometimes the springs break causing problems... hangs up the valve.
TCC apply is not a actual apply like a clutch pack.
Oil on the back side of the turbine gets dumped back into the trans.... this allows the turbine dampener to come in contact with the cover giving you a 1 to 1 connection (lock up) with the engine.
So oil pressure is actually dumped to apply the TCC.
Hope that helps you.

[hoogiesngrinderz]

Solenoid is new, I'll inspect valve while I'm in there. Thanks!

[Detroit Gearbox]

With the solenoid removed, take a small pick or screwdriver and push upward on the valve. It should be spring loaded and move freely, and return all the way down to the washer/retaining clip.