Transmission downshifting issues

Dmf10e · October 17, 2016

Not sure if it's the same issue but I have 2k miles on my 16' v6 engine, 6 speed. I notice when I'm braking or coasting down to about 30mph, the RPM will drop to about 1000 and then jump up to 1100. And you can feel the truck kind of shift and jolt forward. More noticeable in stop and go traffic. Didn't notice it when I first bought the truck, but more noticeable now. Bought it back in June so haven't driven it a lot. Anyone else having the same issues?

Just took it in to the dealer for the airbag tensioner recall and told them about the RPM issue. I'm sure they will just come back and say it's "normal."

Boardmember · October 17, 2016

I've gotten used to it in my 8 speed - horrible - hoping against hope it won't affect reliabilityof my transmission at 40k miles.

Certainly GM is aware. I would like to know if they plan to sit tight or proactively notify customers they will assist if/when needed.

Sigma Nu · October 17, 2016

Same with my 5.3 V8. I'm guessing it might or might not be a torque adjustment or something to do with the solenoid. Please keep us updated. Thanks

Dmf10e · October 17, 2016

I've gotten used to it in my 8 speed - horrible - hoping against hope it won't affect reliabilityof my transmission at 40k miles.

Certainly GM is aware. I would like to know if they plan to sit tight or proactively notify customers they will assist if/when needed.

It is annoying. It isn't THAT bad, but I can definitely feel it. Besides now that I notice it's an issue, my eyes are glued to the tachometer and I notice it ALL the time. It's at the dealer right now getting the recall issue fixed, but I did tell them about the issue. Not sure how long it takes to fix the recall issue, but the longer it is I don't hear back, the more I feel a little better like the fact that they may be finding something wrong...? haha Wishful thinking probably.

nluchau · October 17, 2016

Same boat. My 2016 z71 5.3 has just over 900 miles and did it from day 1. Dealership says that's how they are designed. Let me know what you find out. Perhaps there will be an update for the TCM to make the transition points a bit less noticeable? Wishful thinking?!?!?

Dmf10e · October 17, 2016

I read this on another thread, and they mentioned this Bulletin #16-NA-019. Could be the same type of issue and fix?

#16-NA-019.pdf

nluchau · October 17, 2016

I read this on another thread, and they mentioned this Bulletin #16-NA-019. Could be the same type of issue and fix?

This appears to be for the 8 speeds, definitely might relate to the 6's though too.

InertiaFaze · October 18, 2016

Keep an eye not only on the tach and the V4 / V8 state but also if this happens while coasting or braking, what does the instantaneous fuel economy read? Does it change from 99mpg to something more "normal" at about the same time as the "bump"?

mookdoc6 · October 18, 2016

It was performed on my truck and cleaned it up real nice have not had any issues since!

Sir Dan · October 18, 2016

With my 8 speed, I'm starting to figure out that the harsh or flare shifting (either up or down) nearly always happens when in V-4 mode. Dealer has performed some software update that did nothing. I've started just shifting to manual and setting it to M7 to keep it in V8 until I hit the open highway. So far it's been better but WOW, what a poor quality product for $42 grand.

mookdoc6 · October 18, 2016

Yeah, can be annoying no doubt! I mean it beats a carburetor but......throttle response sucks ass and the v4 to v8 transition is quite smooth just not during the moment it shifts which is why it flares on purpose too! Oh well mine is feeling pretty good now and BLACKBEAR is where I am going the warranty can piss off!

Dmf10e · October 18, 2016

**UPDATE**

So the dealership told me they ran diagnostics on it and it returned no error codes. Said it was the "lack of torque converter" whatever that means and he said it was "normal" which I knew they were coming back with. Which is total BS. How is it that it can be fixed for some trucks and not for others? I was given a 2016 v8 truck as a loaner and it did the same thing, but it wasn't as noticeable. Also made me regret not getting the V8...so much sweeter! Although I love my truck anyways.

nluchau · October 18, 2016

**UPDATE**

So the dealership told me they ran diagnostics on it and it returned no error codes. Said it was the "lack of torque converter" whatever that means and he said it was "normal" which I knew they were coming back with. Which is total BS. How is it that it can be fixed for some trucks and not for others? I was given a 2016 v8 truck as a loaner and it did the same thing, but it wasn't as noticeable. Also made me regret not getting the V8...so much sweeter! Although I love my truck anyways.

Thanks for the update. Figured they would say its normal. My V8 does it in all modes, D, M5, Grade Breaking off, Traction Control off, etc... I must learn to live with it I guess.

sk · October 18, 2016

Read some of the other threads about this. Try disabling Grade Braking. It seems to help some but not completely. And you need to redo it every time you start the truck (it resets when the truck is turned off).

Dmf10e · October 18, 2016

Read some of the other threads about this. Try disabling Grade Braking. It seems to help some but not completely. And you need to redo it every time you start the truck (it resets when the truck is turned off).

Yea. I've tested it with disabling that and it's the same. Seems like it's a "normal" occurrence among these transmissions. Not as noticeable with the V8, but still present.