I have a 2015 Impala with almost 18,000 miles on it now. The last week I have noticed that anytime the transmission goes from 3rd to 4th gear the rpms rise by a few hundred before it will switch. This causes a delay in switching gears. It will do it no matter how I accelerate. I have the trifecta tune but don't think this is the cause as it will still do it when I engage cruise control(tune off). Am I the only one experiencing this issue?
PS. I have the 3.6l v6.
I had the same issue when shifting into 3rd when turning left or trying to pass. Took my car in 3 times to the dealer. Each time they said no issue found and I codes. Just before I took it in for an an change at 47,000 miles, i was checking the air filter and noticed the air tube that goes from the air filter to the throtal boby had a tear in the flex part. After doing a quick fix by using electrical tape until can get a new one ordered. My shifting problems went away. The problem was extra air entering past the air flow sensor and the computer couldn't compensate and add fuel.