The vehicle has a circuit that adds vacuum when the engine is below 50C. Accordingly, the shifts might be a bit smoother in this operating range. The design is to offset the cold transmission fluid which would otherwise result in shifts that are too firm for most folks.

If you've got shifts that are too firm when warm, it's time to get a vacuum gauge on the transmission modulator line and see what you've got at various operating modes.

Otherwise, we're just grasping at straws...........