How does my 727 trans lock up

Converter Lock-up on a 727 is controlled by the lock-up module on the valve body. In the module there is a so called Fail Safe valve which only allows lock-up when the direct clutch is fully engaged (3rd Gear). It also provides a quick Lock-up clutch release in the event of a kick-down situation. The lock-up on a 727 is purely hydraulically controlled, eliminating the need for a solenoid as in the 46RH.