Silverado transmission problems

This was asked by someone a couple of months ago and I was wandering if anyone else has had this problem. My 2000 Z71 is doing the exact same thing. Thanks for the help.
I've noticed when I'm just driving normally the truck shifts fine from 1-2, 2-3, but then when it gets to the 3-4 shift, it seems like it shifts, goes back into 3rd, then shifts again back into 4th. it seems to shift fine. It went from doing this occasionally, to doing it nearly every shift from 3-4.
What could be causing it to do this?

our computers for our trucks are programmed. this includes the transmission shift pionts and firmness. if you do a search on GM Technical Service Bullitens, (TSB's), you'll see a bunch for reprogramming, or "re-flashing" the computer, to relearn it's shift points, all due to customer complaints.

afterwards, it takes about 300-500 miles to get used to, and set for your driving.

mine was done at 550 miles, (slushbox between 1-2 and 2-3 shifts, but only sometimes) at 900 miles, it was sweet. i'm at 13000 now, and it hasn't changed one bit....... :iceslolan

http://www.alldata.com/recalls/

i also know there's a valve in the valvebody that wears it's bore, and causes a similar problem. this is apparently inherant with newer GM trucks. the quote i got was about 350 clams to install the repair kit. the problem usually shows up at about 75k on up for most 4 speed autos...........

here's a dude with the same problem as you:

http://www.automotiveforums.com/vbulletin/showthread.php?t=203346