I had a Metro that would start out in 3rd gear, but would shift manually just fine. Replaced the Automatic Transmission Control Module ( ATCM ) located under the dash next to the steering column and that solved that problem!
I now have a similar issue to the original post here...if my car sits overnight, then when I first start and go, it works perfect, by the time it warms up, it won't shift from 1st to 2nd without letting off the gas after it goes over 4,000 RPM. It also will not go in reverse. I have replaced the ATCM, neutral safety switch and speed sensor. I do believe it is the transmission solenoids, but not sure where they are located ( in the valve body or on the side of the tranny )?
GM Line Rat - I do not see the links to your post showing the pictures of the tranny and solenoid details. Can you please repost?