Hello, I'm new here. I have an '02 2wd Tahoe that when cold you have to shift it manually. If you try to start in OD position, it will just rev like in neutral. Most of the time after it warms up, you can start the engine and put it in OD position and it will go the way it's supposed to. Sometimes even warm you still have to shift manually. Once you have shifted it manually and come to a stop, it will take off like it's supposed to. Any ideas?