2014 - 2018 5.3 6 speed downshift jerks

[nluchau]

My valve body and TCM was replaced already and the taps reset a couple of different times but that was all.  I believe with the valve body the fluid was mostly all replaced?  It's almost like its downshifting too early thus causing the rapid jump in RPM and the jerk/braking sensation because its not matching the speed.  

[Sierra Dan]

Can we all fully blame the Transmission itself?

What about AFM kicking in and out of V4 and V8 while still trying to communicate with the transmission.

Can we blame some of this on AFM ?

I would like to think Yes.

[Delawarefishing]

My 18' has 2000 miles on it and shifts like absolute JUNK. I floored it the other day and from 1st to 2nd there is a long delay. I got frustrated with the jerky clunking shifts . Nice riding truck and built as solid as any brand but the drive lines in these things are garbage. I hear the complaining about feeling the downshifts,  I have that too and that's nothing compared to the crap shifts I get during acceleration.  Sometimes it's not bad, other times it makes you furious that you're riding around in a $45k truck that feels like a $900 pos

[Grumpy Bear]

On ‎10‎/‎31‎/‎2018 at 9:09 AM, crushNchowda said:

So which is it guy? Are they "looser" or are they "stiffer"??? Sounds like more excuses for piss poor engineering & lazy Mexican manufacturing teams - sounds like big cuts & savings in R&D/Engineering/OEM parts suppliers/labor to help pad the balance sheet after borrowing our tax dollars to prevent bankruptcy.

I do wish I had seen this when it was posted. 

 

Question. What is the opposite of 'loose'?  How about tight. Are your nuts loose or tight? Not are your nuts loose or stiff. 

 

Loose or tight are opposites. Tolerances are looser in the driveline of a truck. Yokes splines etc. Stiffer was an adjective describing the chassis, springing and dampening. 

 

Here's the funny part and I don't mean ha-ha funny either. You knew this when you drafted it. You didn't need me to step on. You have  your own soapbox. So what's the point? 

[Mozzer]

Can we all fully blame the Transmission itself?
What about AFM kicking in and out of V4 and V8 while still trying to communicate with the transmission.
Can we blame some of this on AFM ?
I would like to think Yes.

Not AFM from my experience, same shifts if left in M5.

My dealer service tech found a bulletin of some sort that mentioned a clunk during 2nd to 3rd shift when cold (i.e. First shift of the day). Mine does this every morning, winter or summer.

The description was something about bolts inside needing threadlock & retorquing. I doubt this is my problem as it's been the same from day one but I'm going to get it in to the dealer before my 5 year warranty runs out in June.



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[nluchau]

9 hours ago, Mozzer said:

Not AFM from my experience, same shifts if left in M5.

My dealer service tech found a bulletin of some sort that mentioned a clunk during 2nd to 3rd shift when cold (i.e. First shift of the day). Mine does this every morning, winter or summer.

The description was something about bolts inside needing threadlock & retorquing. I doubt this is my problem as it's been the same from day one but I'm going to get it in to the dealer before my 5 year warranty runs out in June.



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Mine has this 2-3 hard shift (first one of the day) too.  Then its fine.  

[TXGREEK]

Can we all fully blame the Transmission itself?
What about AFM kicking in and out of V4 and V8 while still trying to communicate with the transmission.
Can we blame some of this on AFM ?
I would like to think Yes.

Yes! I noticed a difference, using my tuner, turned the AFM back on and immediately noticed the extra clunking, switched it back off and almost zero clunking. I agree with you Dan.


Sent from above

[njk4o5]

wheres all the clowns that say there arent any shifting problems with these trucks now?

[nluchau]

I dont know if the dealer has ever done a clutch relearn on my 6L80,  is that a thing if they reset taps they can do that?  I know on the 8 speeds they reset them and relearn but I hear nothing about the 6 speeds.  

 

The TSB that talks about the 8 speeds having harsh 3-1 downshifts is exactly what I am experiencing with my 6 speed but it seems my issue falls on deaf ears.  This is what I am referring to that doesnt pertain to my issue but I'm having almost the same issue.  https://gm-techlink.com/?p=7170

Edited February 20, 2019 by nluchau

[nluchau]

Duplicate post

Edited February 20, 2019 by nluchau

[greystone]

Something I discovered recently.  If you hold the tow/haul button for 3 seconds it will toggle on and off the grade shifting feature.  Mine was on by default.  I have turned off the grade shifting and have since noticed a significant improvement in transmission performance.   Especially during deceleration.  The clunkiness is almost completely gone. 

 

Give it a try.....

[chrispassas21]

2 minutes ago, greystone said:

Something I discovered recently.  If you hold the tow/haul button for 3 seconds it will toggle on and off the grade shifting feature.  Mine was on by default.  I have turned off the grade shifting and have since noticed a significant improvement in transmission performance.   Especially during deceleration.  The clunkiness is almost completely gone. 

 

Give it a try.....

you have to do this everytime you turn the truck on?

[greystone]

no it will remember the setting

[Mozzer]

Disabling grade braking as above is reset after my truck is restarted, also doesn't change my shift problems, just prevents the down shifts when going down a long hill with brakes applied.

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[greystone]

19 hours ago, Mozzer said:

Disabling grade braking as above is reset after my truck is restarted, also doesn't change my shift problems, just prevents the down shifts when going down a long hill with brakes applied.

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well dang... you're right.  I thought it was staying off.   I guess I can't explain the recent good behavior of my transmission.