I've searched and not found this particular issue discussed anywhere. My torque converted appears to lock and unlock normally (passes Offroad's tests). However, when driving with the TC locked (say 2400 RPM at 65 MPH in 4th), if I let off on the gas altogether, the RPM will drop 400 to 500 RPM (down to 2000 immediately). I know that the TC is locked initially because I can observe the drop in RPM from the unlocked (2700) to the locked state (2400). It just appears to "unlock" again if I let off on the gas. I had expected that the TC would just stay locked (less tranny heating and better engine braking). It'll do it in 3rd as well. Is this normal?

Sorry for the long post. Thanks for your help, Steven