We need a GM tech to log onto GM's site to gain access to the information in the URL listed below.
http://service.gm.com/servlets/BlobShtml?S...+1796287&evc=sm
Document ID# 1796287
In a nut shell....
After a cold soak this slight movement is due to the residual tranmission fluid in the clutch packs that creates a partial apply in start up. This also might be accompanied by a "Clunk" noise.
Goes on to say to use the parking brake as per Owner's Manual.
This effects 3T40, 4L60, 4L60E, 4L65E, 4L80E, 4L85E, 4T40E, 4T45E, 4T60, 4T60E, 4T65E. 4T80E, 5L40E, 5L50E, 6L80, AF225, AF235,LCT1000, M74.
Hope this helps anyone interested.
