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Dan
Dan, Technician
Category: Transmissions
Satisfied Customers: 23590
Experience:  2 Year Automotive Technician Diploma, Independent Shop Experience, and Multiple Database Access.
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We have a 2008 GMC Sierra 1500 and have replaced the

Customer Question

We have a 2008 GMC Sierra 1500 and have replaced the transmission 2 times, and the 3rd has just seemed to go out. All in the last 18 months. And within 20,000 miles. It doesn't shift hard, just gets to really high rpm's before shifting into 3rd and then 4th. We purchased the first replacement from Napa, and the second was under warranty, as will be the 3rd. But there has to be another issue, or this wouldn't be happening. Advice?
Submitted: 12 months ago.
Category: Transmissions
Expert:  Dan replied 12 months ago.

Hello, my name is*****'ve seen mass airflow sensor cause transmission to shift at high rpm's and slip eventually leading to premature transmission failure. Besides that the only thing would be the actual computer which is unlikely. When transmission is fixed again for 3rd time you can see if it shifts better with the mass airflow sensor unplugged, if so replace. Let me know if you have more questions or if there is anything else I can do to help. Thanks.

Customer: replied 12 months ago.
But every time, it runs perfectly fine until all of the sudden, it revs and won't shift. There is no gradual decline
Customer: replied 12 months ago.
also, there are no codes when hooked up to diagnostics
Customer: replied 12 months ago.
Is there any other advice you can offer?
Expert:  Dan replied 12 months ago.

The only thing that would effect shifting is the mass airflow sensor or PCM. When the mass airflow sensor first starts to fail like this it will not usually turn on check engine light either. So I would just replace the mass airflow sensor if you are not having any driveability symptoms. Let me know how it goes or if you have more questions, thanks.

Customer: replied 12 months ago.
What is the pcm?
Expert:  Dan replied 12 months ago.

It is located near/under the battery tray but a new PCM would need to be programmed to vin at dealership. Let me know if you have more questions, thanks.