Problem is in an A999, three-speed with lock-up. Transmission will shift through all three gears while vehicle is at a standstill (I am not kidding). Gage installed in the governor test port will show pressure climbing slowly from zero in Neutral, to about 24 psi when Drive is selected on the column. Takes about two minutes for the pressure to climb, engine idling, and I can hear the shifts taking place in the transmission. Pressure will drop off to zero again when neutral is selected.
If I take advantage of the zero pressure condition by dropping it into Drive and immediately accelerating, I can get a moving progression through the gears, but once in third the transmission will not downshift or return to first automatically, even when vehicle is brought to a dead stop. It will stay in third gear. Manually shifting through the gears, i.e. starting, from Neutral, to D1, and moving shifter through D2 and D3 at appropriate points, results in a normal shift sequence.
I have replaced the governor, governor support and seal rings, removed the valve body and worked every spool with jeweler's rouge till it slides without a hitch. Valve body was assembled and installed to manuf torque specs. Manual valve adjustment is spot on. Throttle pressure adjustment has no effect on the symptoms.
In short, this tranny's governor circuit is receiving unwanted pressure from somewhere in the transmission and shifting prematurely. Any ideas?