My C7 is a 2014 z51 automatic transmission. I’ve been noticing a small shift flare in low gears at low speeds. I read a service bulletin saying it’s normal and not to attempt any repair. Has anyone experienced or heard about this who can shed some light on this condition?

 

My '16 A8 does it at times, and my '07 C6 A6 did it also. Never had a problems with the C6, and at 7K on the A8 all seems well. Probably is a normal occurrence, but I can't say if we are experiencing the same amount of "flare." If possible I suggest you take your baby to another GM dealer just for your own peace of mind. Good luck

 

Okay, what is a "shift flare?" My imagination's runnin' wild!!!

 

Haven't heard that one either.

 

If I am interpreting it correctly it's when changing gears the rpm's increase a bit between the gears. Or, kinda like the first change of the day with an A8.

 

If you mean shift "flare"it means slippage or an increase in engine RPM between gears on acceleration with an automatic transmission. Shift "Flair" is usually followed by a knife edge chop and the crowd going "WOOOOOO"!

 

I don't know if what I have is "shift flare" or not. Sometimes, not always, at low speeds I experience erratic shifting. It usually happens when slowing down for a stop light, and then the light turns green before coming to a stop. When I begin to accelerate it has a hard shift. Not sure I'm describing this well enough for anyone to be able to understand. It’s always between 1st and 2nd gear. Am I confusing the transmission by braking and during the down shift I accelerate? Hope that it is not a serious problem.

 

Apocolips, that is in the shift programming and sometimes the timing works out where you are starting to resume throttle just at the point it is dropping to 1st for a stop. Basically in the middle of one set of steps it is switching to a different set so it isn't as smooth as in a normal shift situation. It is annoying but it doesn't lead to a serious problem. I have had it happen a few times in my 2016 Z06 in exactly the same situation, slowing where it is normally going to stay in 3rd until shifting into first at a near stop but then I am back on the accelerator.

The 8L90 is like all of the other recent GM transmissions in that it uses clutch to clutch architecture to shift between gears so (depending upon the shift) one or more sets of clutch packs is releasing simultaneously with the application of one or more sets of packs that are applying and when the timing is perfect the shift is perfectly smooth. The transmission learns and self-adjusts (for clutch pack wear) over the life of the transmission and over time it will learn from a "bad" shift and adjust apply/release timing and apply force but there will be situations where what it has learned isn't perfect for a situation so there may be a slight flare when apply/release timing isn't perfect.

If the flare is consistent and bad then you should get it to the dealer because this can be due to (and lead to further) clutch pack wear. But minor flare is going to happen at times. I have never noticed flare in my 2016 Z06 but my 2006 GMC pickup (diesel with Allison automatic) developed a slight flare at about 2,000 miles just on a light throttle 2 to 3 upshift while cold with the air conditioning on. I made it go through this shift repetitively several times and it disappeared and never reappeared. The Allison is a much heavier (and heavier duty) transmission but the basic technology is very similar in that it is also a clutch to clutch intelligent transmission that learns from shifts that differ from the desired shift quality.

 

I would like to help, but I don't understand what you mean by between 1st and 2nd. There is nothing between 1st and 2nd. If you are coming to a stop the car should bypass 2nd. It should move from 3rd and directly to 1st. What gear are you in when you begin to accelerate?

 

...............it's all the badges and buttons that Jennifer Aniston wore in "Office Space".

 

 

Thanks Joe, I think that NSC5 explained it better than I did in his first paragraph. It usually happens so fast it's hard to look and see what gear it was in. He explained it very well and I'll just keep an eye on it.

 

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