2019 8speed Transmission temp and shifting issues

[Bobv07662]

Early September 2018 build, 2019 2wd 8 speed 5.3L, transmission temp never exceeded 170, now while driving same route and conditions the trans temp is 185 and the 1-2 + 2-3 light throttle shifts are slide/ bump affairs and the corresponding downshifts are very harsh. Started all of a sudden. Very repeatable. When the trans temp is below 175, it upshifts and downshifts fine. Warranty still in effect, fluid never updated to the newer Mobil 1 version.

Anyone have any experience similar to this? Thanks for any insight.

[Gangly]

If warranty is still in affect, take it to the dealer and have them assess the issue.  Most likely you will get a transmission fluid flush, or at worst a fluid change.  My guess would be transmission fluid breakdown is the reason for the elevated temperatures.

[bigdoug42]

My trans temps regularly exceed 200 degrees especially during stop and go, don't have any of the shifting issues. My truck is a z71, same build date, same engine, have no idea if it was upgraded to the Mobil 1 fluid. 75 percent of my driving is rural though.

[Bobv07662]

Thanks to all...will be in dealer's hands next week. Will keep you posted.

[Bobv07662]

Sorry I haven't given an update .... I wanted to drive the truck on the exact route with the exact same load before reporting back. 

The fluid was flushed and the transmission software was updated.  Now the transmission temperature never exceeded 175'F and all 1-2 and 2-3 shifts are on time and feel fine. The 3-2-1 downshift is smooth and no longer harsh. Amazing that a fluid change could make such a difference!