Blend door is bad and needs replaced
I unplugged the battery several times. I also cycled the climate controls and that didn't work. I also checked the driver's blend door. That was working.
I dropped it off at the dealer today. I am having them check the following:
1. Transmission clunking on down shift.
2. Transmission lazy shifting when at low speeds.
3. Engine rattle when cold.
4. Low fuel mileage. (last 3 months it has gotten 4 mpg less)
5. Rear diff is not unlocking properly when at low speed.
I also contacted Chevrolet Corp to get a case number and to let them know that I am very unhappy with the property. I have had two of these Tahoes. One GMT800 and one GMT900. Both had similar issues. Not sure what will come of it. Worth a try.