2014 Silverado crew 5.3 4wd 6L80e

Truck has been clunking with downshifting for a while, mostly 3-2 but some in other gears as well. It just started slipping (seen in the vid) however in the past 2 days. Powertrain warranty is still good until 10/19. I wasn’t sure if I was dealing with a Ujoint or transmission issue until this started happening. It certainly looks like a slipping transmission to my untrained eye. Truck was bought second hand but appears to have had an easy life. To my knowledge the transmission has never been serviced, however manual doesn’t recommend until 97K. I checked fluid levels and it was within the marks and as you can see the temp is within reason. Looking for input from the forum experts so I can do more homework before taking it to GM garage this week. Thanks.

 

Forget the manual. it is my firm belief that all automatic transmissions should have the fluid changed every 50,000 miles, even less if you have a tranny with a non-replaceable filter like the new 6T40e as I have in my 2015 Malibu or you are doing lots of stop and go city driving. Just changed the fluid last week at 27,000 miles and although it was dirty it was much cleaner then when I first bought it used at 40K. Still had a reddish color to it, no metal. Shifts very smooth, no problems whatsoever.

If you are going through lots of dust or water crossings I'd drop it don't to 30k minimum. Since you have a warranty why not use it since you paid for it?

 

Thanks oilcanhenry, that’s good advice. I will definitely be more aggressive with changing in the future. My concern is that GM garage will try to put a band aid on it (like simply changing the fluid and filter) and the warranty will run out before it totally craps out. Even with original fluid I don’t think the transmission should be slipping and knocking at 80K. I have an appointment in a week to get a formal diagnosis.