2000 Z71 Transmission Problems

I have a 2000 Z71 with a 4.8L engine. When I drive it for approximately 30 minutes, stop, then take off again from a dead stop, It shifts extremely hard from 1st to 2nd. I have recently had the
transmission rebuilt, as well as replaced the torque converter, but I still have the same problem. I was instructed to replace the Throttle Positioning Sensor, which I have a hard time understanding that suggestion. Anyhow, I replaced the TPS, and the problem still exists. If I shut the engine off for 30 seconds the problem goes away. I can drive another 30 minutes and the problem returns. It only happens after a somewhat lengthy drive. Could my governor be defective, or is it something else?
Thank you.
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On 25 Feb 2007 21:19:28 -0800, snipped-for-privacy@sbcglobal.net wrote:

It has a electronically controlled tranny and engine and sensor performance plays a roll in how it shifts. Have you scanned it for OBD2 codes and is this hard shift also delayed as well? ----------------- TheSnoMan.com
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is the check engine lite on(or on now and then). Sounds like an po1870 GM Tranny code to me.jp

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My '99 Yuk's trans will go into a tow mode if I drive it hard. IE lots of heavy on the gas shifts not easy driving light on the throttle stuff. Shut it off and restart and it returns to "normal" mode until I start hammering on it again. The auto tow mode will make the 1-2 shift super firm. Check the owners manual and see if your truck does this. My truck does not have the tow switch of the later model trucks, I think that's why they went to the tow switch and got away from the auto tow mode. Screwed up TPS fooling the trans into tow mode? Maybe that's why the change it suggestion. Some sensor is bad fooling it into tow mode is my shade tree guess.......

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