Thanks for reply.
It's an 2001. Lock and unlock is at the slower speeds, less than 47 MPH. Let up on accelator and it unlocks, give it accelerator and it locks.
When above 47 MPH, it unlocks when it start to pull, not too heavy. The engine will simply not lug down and let the RPM's decrease with MPH.
Perhaps unfair to compare to my 96, but the converter locks at about 30 MPH and will stay locked even after shift to OD. It stays locked until manually released or I can lug engine down to near 50 MPH before auto unlock. Maybe this is the differance between the old manual fuel control and the newer electronic.