My dad bought my old truck it's a 2000 z71 with a 5.3. He had the tranny rebuilt by a shade tree guy. He goes to put it in drive takes off great has first and second but no third or drive. Then he goes to put it in reverse and its goes forward and when you give it gas it goes backwards and tries to pull forward as we'll. So he gets a new tranny from a wrecked truck still same problem with no third or drive. He changed filter and the fluid as well as the PCM.



Any ideas?