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Possible Shudder? - 2018 Sierra 1500 5.3 8-speed

Marc Rocca
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Marc Rocca New Member

Marc Rocca

Posted
Posted

Hello All,

 

New to forum and looking for some advice....

 

I have a 2018 Sierra 5.3 with the 8-speed, 63,500 miles.  About a month ago, while driving around at light-medium throttle I get an intermittent shudder thru the truck that feels very much like driving over a rumble strip.  Sometimes it lasts for only ~0.5s, sometimes it may last 3 to 5 seconds, the longer instances are less common.  Overall it only happens occasionally...maybe once every 3-5 min on average, but sometimes I'll get a few distinct occurrences back to back to back.

 

The part that is curious, is that even when stopped (at a red light or stop sign)...I get a very brief shudder that causes the engine RPM to drop to ~450, but only lasts for less than 0.5 second and is immediately recovered to the normal 500rpm at idle and idles dead smooth from there.   On average this may happen only a few times when stopped at the average red light.

 

I took it into a local dealer and after two days with the truck they came back with a diagnosis of a misfire on cylinder #2 and recommend replacing plugs/wires.  There is/was no CEL then or now.  I replaced all 8 plugs (old ones looked good to me), the wire and ignition coil for cylinder #2.  The problem still persists.

 

3 months ago (before I had any of these problems) I had the intake cleaning service (including throttle body) performed at the end of my CPO warranty.  The truck ran so smooth that sitting at idle you had to look at the tach to now it was on.

 

I have logged some data in my scan tool and will post once I find the cable to download it to the computer.

 

Thanks for any help/advice...

- Marco

 

 

 

 

JimCost2014 Senior Enthusiast

JimCost2014

Posted
Posted
34 minutes ago, Marc Rocca said:

Hello All,

 

New to forum and looking for some advice....

 

I have a 2018 Sierra 5.3 with the 8-speed, 63,500 miles.  About a month ago, while driving around at light-medium throttle I get an intermittent shudder thru the truck that feels very much like driving over a rumble strip.  Sometimes it lasts for only ~0.5s, sometimes it may last 3 to 5 seconds, the longer instances are less common.  Overall it only happens occasionally...maybe once every 3-5 min on average, but sometimes I'll get a few distinct occurrences back to back to back.

 

The part that is curious, is that even when stopped (at a red light or stop sign)...I get a very brief shudder that causes the engine RPM to drop to ~450, but only lasts for less than 0.5 second and is immediately recovered to the normal 500rpm at idle and idles dead smooth from there.   On average this may happen only a few times when stopped at the average red light.

 

I took it into a local dealer and after two days with the truck they came back with a diagnosis of a misfire on cylinder #2 and recommend replacing plugs/wires.  There is/was no CEL then or now.  I replaced all 8 plugs (old ones looked good to me), the wire and ignition coil for cylinder #2.  The problem still persists.

 

3 months ago (before I had any of these problems) I had the intake cleaning service (including throttle body) performed at the end of my CPO warranty.  The truck ran so smooth that sitting at idle you had to look at the tach to now it was on.

 

I have logged some data in my scan tool and will post once I find the cable to download it to the computer.

 

Thanks for any help/advice...

- Marco

 

 

 

 

Welcome to the site.

 

I just developed the "shudder" recently. Took mine in for the transmission TSB with the new Mobil 1 Blue Label fluid. Shudder is gone, feels like a new truck. If you have not serviced the trans yet, would strogly suggest doing so. 

NWI Denali Enthusiast

NWI Denali

Posted
Posted

You have 2 different, unrelated issues going on. What you have while driving is 100% the trans shudder. There is a TSB for a fluid exchange with 20qts of the new Mobil 1 ATF. This would be covered under your powertrain warranty. However, you being at 63k miles is a grey area... if you have a good dealer, I'm sure they could get it goodwilled for you through GM.

 

The stumbling at idle is a completely different issue on its own. You already did plugs and wires. Only other thing I could think of is to clean the mass airflow sensor.

JimCost2014 Senior Enthusiast

JimCost2014

Posted
Posted (edited)
On 12/28/2021 at 9:43 AM, Ray L Fitz said:

Do you happen to know the TSB number, I have the same situation.

This is the one that was done to my 2018.

 

TSB (Technical Service Bulletin) 18-NA-355

Edited by JimCost2014
  • Like 1
S W New Member

S W

Posted
Posted

I also had this shuddering problem on my 2017 8-Speed, as well as while driving at low highway speeds (50mph) in high gear, if you watch the tach, you will see it occasionally drop slightly, then back to normal 3/4 of a second later, indicating the torque converter 'slipping'. I took it in to the dealer where they performed the TSB of the fluid change - I was extremely skeptical, but that fluid change (to a different type fluid) completely solved all the problems, and they haven't returned several years later. Good luck.

  • Like 1
pokismoki Senior Enthusiast

pokismoki

Posted
Posted (edited)

does it shudder in all gears?

 

you can also loose TCC lock up if the o-ring on the snout of the oil pump has been over heated, it because cracked and shrinks from heat. this stops sealing the tcc in the converter giving you a shudder or no lock up

Edited by pokismoki

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