Q: hello i have a 2000 sierra 5.3 idling high and tranny shifts when its idling high seems like it does it when its warmer weather tu

If I am understanding your question correctly, it sounds like the engine is idling high, but I don’t understand the transmission issue you’re having. The high idle is most likely an intake manifold vacuum leak at the gasket O-rings. This is pretty common and would require the engine intake to be removed to fix it. The idle air valve is another possibility and would require the computer be tested to see if this is the cause. I would recommend having a mechanic, like one from YourMechanic, come out and diagnose the high idle and and transmission issue you are having.