It sounds like you are thinking of the 1996 - 2000 (or so) GM "Autopark" system. In this, the emergency brake is held on by a very strong spring. When you move the tranny lever out of Park, a hydraulic pump runs and releases the spring. There is a reservoir for the ATF used in this system. Also, the control switches can leak fluid and the emergency brake can come on at inopportune times.
George Schweikle Lexington, KY
1999 Safari TREK 2830, FMCA 190830, Safari International chapter
1995 Safari TREK 2630, 1983 Winnebago Chieftain, 1976 Midas Mini