Staffan,
Is it doing this in both directions? Do you have any pressure readings for the Pump and Clutch Pack? You may be fighting one of two things. (1) A bad Torque Converter (2) Possible restriction in the Control Valve you installed, either the gasket was incorrect or positioned improperly.
Let me know
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.