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Just got a new ‘18 GMC Z71

dsm1995gst

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dsm1995gst Enthusiast

dsm1995gst

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Especially on downshifts... you can feel every downshift and often times it’s like it’s downshifting too early and it’s almost like the truck nosedives a little.


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jguzek Enthusiast

jguzek

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Dsm, what size engine and transmission?

My 18 GMC Denali 6.2L- 8 speed was terrible when I first got it. Felt like a bucking bronco.

4 months later with about 5,000 miles on it it's hardly noticeable.

I thought it was a bunch of BS when the service department first told me you need to give the transmission time to "Learn" , but there seem to be some truth to it in my case.

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Capt Bob Enthusiast

Capt Bob

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Well I remember Chevy gave you a VHS tape in your 03 2500HD to get you prepared for an Allison trans. It had to "learn" your driving style every time you replaced your batteries (Duramax) and they really didn't last that long. Rough riding, hard shifting and cabin noise was just part of the ambience of that truck. I loved it and I guess it spoiled me for my current ride. Smooth (for a truck) and quiet.

Guess I'm one of the lucky ones. 

wforrest08 Senior Enthusiast

wforrest08

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There’s pages and pages of threads on both trannys.

 

My 015 was shifted so stupidity that I decided F it and did a tune at 3k miles cause I couldn’t stand it anymore I wasn’t going to go full mod till I was at least out of bumper 2 bumper but decided it was that or I don’t really want this thing. 33k miles later on the tune was the right decision for me anyway it’s 92% better every once in a while it still does a funky down/up shift but at least now it’s tolerable. 

 

Like stated above drive it awhile and see some claim it gets better with some miles? After 2900 I was done waiting...

Yondu Enthusiast

Yondu

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Posted

My 18 was a little clunky to downshift the first 500 miles.  Only at 950 or so and it's a lot better.  

 

Also, you may be noticing the gas pedal flex.  Look up gas pedal flex paint stick mod. Takes 5 minutes and it makes driving using light throttle a lot better. 

dsm1995gst Enthusiast

dsm1995gst

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My 18 was a little clunky to downshift the first 500 miles.  Only at 950 or so and it's a lot better.  
 
Also, you may be noticing the gas pedal flex.  Look up gas pedal flex paint stick mod. Takes 5 minutes and it makes driving using light throttle a lot better. 

Hmm, what do you mean by gas pedal flex?

Regarding light throttle, I have noticed that when I start from a stop I give it the amount of throttle that seems appropriate for accelerating lightly and then it seems to sort of start to lag as the RPMs get higher...


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Yondu Enthusiast

Yondu

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5 minutes ago, dsm1995gst said:


Hmm, what do you mean by gas pedal flex?

Regarding light throttle, I have noticed that when I start from a stop I give it the amount of throttle that seems appropriate for accelerating lightly and then it seems to sort of start to lag as the RPMs get higher...


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Mine was annoying until I did this.  I got a fair amount of downshift clunks at first but the transmission seems to have figured things out.  I'd like to do a tune, but this is the first brand new vehicle I've had so I want to keep the warranty a bit longer. 

 

BigBadSierra Senior Enthusiast

BigBadSierra

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The transmission has to go through the learn Phase only issue is who drove it before you??  Try disconnecting the Neg battery cable for 10 minutes this will reset it.

Then it will learn you and how you drive.

 

I'm picking up a 2018 Z71 Crew on Thursday but it was a little Bucky during the test drive but settled down. I will probably have to do this to mine when I get it.

 

I've just pulled the battery cable on my 2016 from time to time to get the transmission to behave.

dsm1995gst Enthusiast

dsm1995gst

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So this is a truck you bought without a test drive?
 
Shakey

No I definitely drove it before buying it and didn’t notice any of this. I’ve got about 1000 miles on it and it has only become noticeable in about the last week.


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dsm1995gst Enthusiast

dsm1995gst

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The transmission has to go through the learn Phase only issue is who drove it before you??  Try disconnecting the Neg battery cable for 10 minutes this will reset it.
Then it will learn you and how you drive.
 
I'm picking up a 2018 Z71 Crew on Thursday but it was a little Bucky during the test drive but settled down. I will probably have to do this to mine when I get it.
 
I've just pulled the battery cable on my 2016 from time to time to get the transmission to behave.

I bought it new.

I have seen a lot about it learning how you drive, but I don’t know how noticeable downshifting is ever appropriate, no matter how someone drives.

Either way, I guess I’ll wait some and hope it goes away.


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Pearl2017 Enthusiast

Pearl2017

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During the learning process I highly advise you to be as smooth as possible with the throttle and brakes as you drive around. If you treat the throttle and brakes like on/off switches the computer will learn to shift that way.

 

If you have Max Tow best advise on that is to disengage the engine braking. On mine that completely removed all clunking/downshifting. My guess is though i will use up the brakes quicker.

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