I have a 2016 Suburban Z71, 89000 miles. It has started shifting like it does in tow mode, only not as aggressively. Almost like a sport mode. Holds gears a bit longer when accelerating and when decellerating it shifts down through the gears so that you feel it. Any thoughts?
Thanks.

 

Has the trans. fluid been serviced it it ?

 

Update-Took it in for service and the diagnostic showed multiple cylinders missing randomly. Turned out that the plug wires were loose in the coils. Apparently someone had changed plugs at one time and pulled some wires loose. This corrected the engine misfire and the transmission returned to acting normally. All these electronics seem to talk to each other in strange ways. Sometimes I miss the Quadrajet, points and condenser, and TH400 transmissions!