Weirdest thing

[chrismoore701]

I got my 79 stepside on the road tonight after my 8 year build. And the Trans is acting strange. I have it hooked up to the base plate vacuum. When I first fire it up and drive it. It will not shift until I drive it at least 4 blocks or so. Even after I drive it and it shifts good for a while. If I shut it off and then fire back up and drive. Same thing. At least 4 blocks. You would think maybe it was due to warming the Trans up. Put about 20 miles on her tonight. Picked up a new control module. See if that does anything. I pulled a vacuum and it held. So not sure