OT- 2000 Chevy Truck Trans. (Brokenwrench can you

Don’t think your dealer has never ran into this before because he is trying to lead you down a very expensive road and like Brokenwrench says, there simply is nothing wrong with your transmission.

Think about it. The tranny isn't going to be defective and then somehow magically fix itself every morning only after the engine warms up.

Have your favorite mechanic put his scan tool on the truck. Watch to see when it comes into loop. It shouldn’t take long; roughly 1 ½ to 2 minutes. If memory serves, in about ’99 or 2000, GM changed that threshold down from 151 to (I think) 95 degrees to lessen cold start emissions.

Since that transmission defaults to second (both solenoids off), it will never upshift past second until the PCM gets off the chair and starts throwing commands.

Don't know what engine/transmission you have, but there will be two temperature send switches. If you’re convinced that your thermostat is okay (not stuck open), I'd be for checking the small send switch with the multiple wires.

That’s the boy that gives control over to the computers when the time is right.

Not trying ot nose into your thread; just trying to help,

Allan

I did the same exact thing; took every blessed class I could find on automatics. Since I worked 95% on GM, of course I was forever in the front office yammerin' for another tranny school thru GM.

Oftentimes, if I ran into something I couldn't handle, I would call in direct to the tech center in Minneapolis and talk one-to-one with the instructor.

Used to be a lot of these guys would just throw in another transmission hoping to "cover the problem"; doesn't work that way anymore. :>)

Allan