what controls the car to shift?
 

after i got my tranny rebuilt my car is stuck in 3rd gear... I can manually shift the cars and its fine,what controls the shifting?
i know all the clutches are good and help?

Ifits a 4L60E its the computer, if its a 700 or 400 or 350 its a combo of the valvebody, and governor.

Modify that, there are solonoids in the valvebody of the "E" that help in that as well. But its all rpm or mph based.

Your '94 has the 4L60E (unless you've changed it). If NOTHING else has changed and the only thing done was the transmission rebuild, then it probably wasn't rebuilt right. Or, you might even have a cracked transmission case, which a general rebuild wouldn't catch even if it was a good rebuild. Also, if it had to be rebuilt because you burned up some clutch packs and the converter wasn't replaced or cleaned out during the rebuild, pieces of clutch material could have been pumped through a fresh rebuild.

Just some thoughts....

If it's an E then check the wiring harness to the tranny. Maybe a pin got pushed in or bent at the plug.