Jump to content

2014 - 2018 5.3 6 speed downshift jerks

nluchau
 Share

Recommended Posts

nluchau Enthusiast

nluchau

Posted
  • Author
Posted

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.  

  • Replies 98
  • Created
  • Last Reply

Top Posters In This Topic

Popular Days

Top Posters In This Topic

Popular Days

Popular Posts

nluchau
nluchau

My 2016 5.3 6 speed has me very frustrated to say the least.  I know I've brought this up before but I need to again. I am still getting the jerk downshifts when coasting/slowing to a stop.  I don't h

nluchau
nluchau

No problem!  Seems to be a widespread issue with no resolution.  

btj_z71
btj_z71

Go for a custom tune like black bear.  They tune the ECM and TCM.  Will update the transmission tables too, makes a huge difference.   Another option is to check all the fluids in your drive

Posted Images

Sierra Dan Senior Enthusiast

Sierra Dan

Posted
Posted

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.

  • Like 1
Delawarefishing Enthusiast

Delawarefishing

Posted
Posted

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 Senior Enthusiast

Grumpy Bear

Posted
Posted
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? 

  • Like 1
Mozzer Enthusiast

Mozzer

Posted
Posted
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.



Sent from my Moto Z2 Play using Tapatalk

  • Like 1
nluchau Enthusiast

nluchau

Posted
  • Author
Posted
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.



Sent from my Moto Z2 Play using Tapatalk
 

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

TXGREEK Senior Enthusiast

TXGREEK

Posted
Posted
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
  • Thanks 1
nluchau Enthusiast

nluchau

Posted
  • Author
Posted (edited)

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 by nluchau
greystone Enthusiast

greystone

Posted
Posted

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 Enthusiast

chrispassas21

Posted
Posted
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?

Mozzer Enthusiast

Mozzer

Posted
Posted

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.

Sent from my Moto Z2 Play using Tapatalk

greystone Enthusiast

greystone

Posted
Posted
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.

Sent from my Moto Z2 Play using Tapatalk
 

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

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Latest Articles

  • Posts

    • AidenVorpagel
      cam upgrade in CA

      By AidenVorpagel · Posted

      hello I recently bought a 2012 gmc 1500 with a 5.3 and have a AFM disabler on it I'm interested in doing a cam but I'm worried if I remove the AFM system I will fail smog does anyone have info if they are able to detect that or a work around to it (not talking about hot smogging) please let me know thank you  
    • B14Sierra
      Noise after AFM delete

      By B14Sierra · Posted

      Did you figure it out?
    • B14Sierra
      Possible lifter tick after DOD delete

      By B14Sierra · Posted

      Update. I started chasing down my symptoms. Started first with pulling valve covers and looked at everything. Everything looked good and couldn't hear or feel anything different. Then a compression test. 240 psi or really close on each cylinder. I was worried I was a tooth off of timing. Not bad for an engine with 173,000. Granted I did put new heads on. I sprayed water around the injector area to see if I could hear a change. Nothing. I hooked up my new hp tuner which I should have done in the first place but I don't really know what I'm looking at just yet but am learning. I noticed the fuel trims were way off so that told me I have to have either a bad injector or exhaust leak. New injectors, so I did the shop vac on blower and in the tail pipe. Sprayed soapy water and found the exhaust flange on the drivers side was leaking. I didn't think it would be that considereding I pulled the heads and left the manifolds attached. I did have the transmission replaced not long ago. They must have not seated them properly but I guess I didn't notice. I put in new gaskets on both sides. Which by the way isn't a bad job but I had a hard time getting them to seal right. Took two attempts. Reset the fuel trims and the ticking is gone, engine runs smooth and acceleration has improved. Got to feel the real difference with that stage 1 cam. It's not that big of a difference but it does add a little more. It feels like how the truck should have been from the factory.
    • Grumpy Bear
      Some Assembly is Required

      By Grumpy Bear · Posted

      Can it still be Assembled I?    Stribeck says that we need a certain amount of viscosity under conditions of load and velocity to prevent two surfaces of a know roughness from tearing each other asunder. And we have marketing trying to tell the masses that those two surfaced require less of that commodity due to more exact limits being placed on the same old clearances. We also know that there are limits to how hard something can before it becomes to brittle to be viable and to smooth to 'wet' the surface and that both of those conditions have been known and met since about the Second World War.    That viscosity value shook out at 10 centistokes at 212 F just under a hundred years ago.  Give this a look: [Anton Parr]     What is advertised is the Kinematic viscosity (mm2/s) or that which has been density adjusted but the value we are after is the dynamic viscosity (mPa.s) or true viscosity. You can see that this number is dependent on density thus base stock and temperature. You can also see that an SAE 30 doesn't reach that value in this example. However an SAE 30 that is at the upper end of the SAE 30 range; 12.5 cSt (mm2/s), might. 12.5 * .83 = 10.375 (mm2/s). If you could find an SAE 30 at the upper end these days.   Then there is the complication of viscosity modifiers or VII or VM, whatever you wish to call them. Polymers added to very thin base oils, perhaps 3 to 6 cP oils, that will meet the SAE *W30 spec at 'tested' shear rates and 100 C/212F  target temperature. So a polymer fortified base that is a fraction of the 10 cP requirement Stribeck insist upon.   This could be all well and good if those polymers didn't have two very problematic 'features'. They shear or loose viscosity both 1.) permanently and 2.) temporality. And they do both omitted in the advertised data with the distinct  purpose of deceiving the consumer of the actual operating state of the fluid. I've shown the example of Warren Oils COSTCO 10.91 cSt 5W30 formuation several times where the 100 C HTHS value is 6.9 cP!! That's the temporary shear down and with and SSI or shear stability index of 9.4 cSt. Note the intentional deception in using mixed units?    After a short while that 9.4 cSt oil has a viscosity corrected dynamic value of 7.8 cP. But as the SSI is still within the range of an SAE *W30 whose lower value is 9.3 cSt.    This allows them to continue to call this SAE 16 weight oil a 30 weight, the cake, and still meet the API requirements for fuel efficiency IMPROVEMENT mandated by the EPA. The eating of the cake. By the time you've worn out your motor doing the responsible thing by adhering to the warranty requirements, (the stick), you get deprived of the carrot, wear control. So sad, to bad.   So what can be done? Do I need actually say? [Anton Parr]       Even this must be monitored if the oil is on the low side and the VII an organic or you opt for a 0W40 with an even lighter base oil and more / higher MW VII. (Note the lower density of the 40 weight versus the SAE 30 mono-weight?)    There is another workaround. Temperature. An SAE *W30 run at a bulk temperature of between 180 and 195 F.    Being the belt and suspenders sort I am I do both. Run it cook and run it heavy.    In Part II I'll work the AW package. 
    • Atlas
      Wow I'm in a pickle. (Broke down truck) and a story.

      By Atlas · Posted

      So, do I go elbow-deep on this thing or list it for sale and play dumb? Seems to "runs good."   I'm about $1200 away from having: -a rebuilt injector ($300) -a new cat ($250) -a new cat back exhaust (OE style) ($300) -a new AC compressor ($200) -AC refrigerant charge ($150)   In theory, this should rectify the obvious detracting issues from its value and operability. Cold AC with a non-squeaking AC pulley both sounds and feels good. An exhaust that isn't cut/hacked in 17 different places and doesn't vibrate on a crossmember would make it sound and feel less janky. A working cat would help the stink, and will save the earth, but *if and only if* the fuel system is working properly, which would also address the intermittent "rich" CEL.   Heard a good one... CEL for "Rich condition" means you haven't spent enough money on the truck lately, and it's letting you know.   Rebuilding the injector would seem to be the most important part. Replacing the cat would be secondary. I don't think mine is plugged or overly restricted, but it might be a little restricted? I have no good way to tell other than seat of the pants feel. I hate the smell.   The current theory is I have a rich idle problem: A bad fuel pressure regulator, or a leaking injector(s) being the highest probabilities. I already replaced the FPR but that doesn't mean its replacement isn't also bad. It was a new part from Dorman, but the packaging looked like it had been sitting on a shelf for 20 years.   This is the (single) upstream O2 sensor shown at idle. I'm getting a lot of "rich" it seems. Sometimes it stays high like that and doesn't drop down. That makes me think it's processing injector leaks or a partially stuck open injector.     Other times it looks like this. Nice oscillations between rich and lean, which is what I think it should be. Under load and at speed, the oscillations are nice and tight and uniform looking, high and low.     Fuel trims suggest the PCM is compensating pretty hard at idle to pull fuel out. But it's not enough to trip a CEL. Something about slowing to a stop: brake vaccum booster, EGR, or the EVAP purge is delayed, or there's pooled fuel in the intake again that's draining into a cylinder is enough to set the CEL. Of course, in two days of driving, it hasn't set. I was hoping to actually look at the freeze-frame data when it sets. IAT is high because it's idling on an 83 degree day here.  

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...