2004 Bonneville Intermittent Hard Shifting

The transmission shifts hard after using for a while, sits for about an hour, then starts to shift hard mostly on 3rd and 4th gear. Then if it sits for a while, it shifts normal. Doesn't do it every time I drive it. I've replaced the Pressure Control Solenoid and the Kick down solenoid. Was running normal for about a week and then it starting shifting hard again. It does not throw any codes.

When it shifts hard, do you here a whining noise? If so, you probably have a P1811, which is Max Adapt / Long Shift. This code will NOT set the SES light but will disable all adaptive shifts and will max out line pressure in the transmission which causes the harsh shifts and cause the transmission pump to whine. This happens because, the pump is supplying fluid at an increased pressure which puts more stress on it, thereby creating the whine. Usually, when you shut the engine off, it will make this condition go away until you drive it again a few miles, or when the engine & trans both warm up and the harsh shifting returns. Click Here (http://www.automotiveforums.com/vbulletin/showthread.php?t=899929) for some DIY tricks. If the suggestions mentioned in the thread don't work, it may be time for an overhaul.