Shudder/Vibration Issue

AdioSS · February 7, 2019

Guess I should take my ‘18 6.2 8 speed Z71 GMC in to get the fluid flushed.

bigman32hockey · February 7, 2019

I don't think GM will cover the cost of the flush if you aren't experiencing the shudder. The technician has to take the vehicle for a test drive and measure noise (or whatever they measure) with a picoscope. It essentially proves whether what you are feeling is the actual shudder or something else (like engine going from V8 to V4, tires, etc.). When the technician showed me mine, the graph looked like someone who was having a massive heart attack. I had huge peaks and valleys all over the place. GM requires the dealerships send this to them before they are reimbursed for the service. Being as it takes about 20 quarts of the new Mobil 1 fluid, I highly doubt GM will pay if it's simply "preventative". But then again, you never know. I definitely wouldn't pay for it out of my own pocket. Be thrilled you're not one of the ones with the issue!

ajensen383 · February 7, 2019

What is the consensus of feeling your truck downshifting into 1st?... My truck feels like it doesn't actually downshift into first when coming to a stop...It hard to explain, but the easiest way is that it feels like the truck goes into netural and (lurches) when I just about coming to a stop, or pull into my garage very slowly. I can even hear the exhaust change note when it does this, the rpm (seems) to drop and exhaust note seems to flatten out, unlike what I am used to when downshifting into 1st the rpm usually goes up... My 2011 and my wifes 2014 tahoe downshifted into 1st normally, even my wifes new 2019 traversed I could feel the downshift and slow down from the shift... this just seems very strange to me...I can feel it downshift it normally when it goes from 3rd to 2nd, but this 2nd to 1st downshifting thing really bothers me..

When it does this and I get back on the gas, is when it will spool up a little then grab 1st gear...

How many of you guys have the same issue??

TRKLGND · February 7, 2019

32 minutes ago, ajensen383 said:

What is the consensus of feeling your truck downshifting into 1st?... My truck feels like it doesn't actually downshift into first when coming to a stop...It hard to explain, but the easiest way is that it feels like the truck goes into netural and (lurches) when I just about coming to a stop, or pull into my garage very slowly. I can even hear the exhaust change note when it does this, the rpm (seems) to drop and exhaust note seems to flatten out, unlike what I am used to when downshifting into 1st the rpm usually goes up... My 2011 and my wifes 2014 tahoe downshifted into 1st normally, even my wifes new 2019 traversed I could feel the downshift and slow down from the shift... this just seems very strange to me...I can feel it downshift it normally when it goes from 3rd to 2nd, but this 2nd to 1st downshifting thing really bothers me..

When it does this and I get back on the gas, is when it will spool up a little then grab 1st gear...

How many of you guys have the same issue??

You described my 2018 6.2 8 speed 2 to 1 shift perfectly.
I have also noticed that when I remote start the truck then put the key in and turn it to the RUN position the truck twitches (jerks is too strong of a word) just a bit as if the TCC engages and disengages in about 1 second.

The 2 to 1 shift is annoying and can be modulated a bit by taking my foot off of the brake for a half second just before the truck stops then reapply the brake. Seems to avoid the "neutral" feeling.

Edited February 7, 2019 by paracutin

hypntyz · February 8, 2019

I have an 18 sierra denali 6.2 bought new in march with 6800 miles on it now, and it seems like I'm one of the lucky ones without the shudder based on the descriptions I am reading here. I do distinctly feel the grab and release of AFM/V4 mode but otherwise it seems relatively smooth. There are very specific circumstances at low speed when the trans seems jerky. Such as if I'm rolling to a stop sign from say 20-30mph and I slow down to maybe 10-5mph but not completely stopped, then I apply throttle to pull out and accelerate again. The trans jerks and its as though it isn't sure what gear to be in for a couple of seconds.

Also I park at the bottom of my driveway so every time I get in to leave I have to climb a bit of a hill, a couple of times it is like the trans is in neutral until I give it more throttle then suddenly it grabs and jerks and takes off abruptly until I let off the throttle. One time I got in and pulled it into D and gave it gas and nothing happened at all, it was completely in neutral with the engine free revving under throttle even though the dash indicator showed D. I put it back in P then back to D and it went normally.

Other than those two oddball issues, my trans seems okay. I would still like to change the fluid just as a preventative measure, even if that means I have to pay for it and do it myself.

I did inquire at the dealer about the possibility of evaluating it for a fluid flush for the known issues, and the service writer told me something like "we cant do anything, gm isnt sending us any fluid until spring" which sounded like BS.

bigman32hockey · February 9, 2019

This is exactly what I feel as well. It makes it difficult to come to a stop smoothly. I thought the new fluid would help with it, bit unfortunately it hasn't made any difference. It's like ones the truck is ready to downshift to first gear it let's go. So you have this resistance you can feel as you almost come to a stop, then all of a sudden you dont. I've never had this in any of my other Silverado's. Man...I should get just kept my 2017. None of the issues I'm having with this one. Live and learn.

SS502 · February 9, 2019

On 2/7/2019 at 11:44 PM, hypntyz said:

I have an 18 sierra denali 6.2 bought new in march with 6800 miles on it now, and it seems like I'm one of the lucky ones without the shudder based on the descriptions I am reading here. I do distinctly feel the grab and release of AFM/V4 mode but otherwise it seems relatively smooth. There are very specific circumstances at low speed when the trans seems jerky. Such as if I'm rolling to a stop sign from say 20-30mph and I slow down to maybe 10-5mph but not completely stopped, then I apply throttle to pull out and accelerate again. The trans jerks and its as though it isn't sure what gear to be in for a couple of seconds.

Also I park at the bottom of my driveway so every time I get in to leave I have to climb a bit of a hill, a couple of times it is like the trans is in neutral until I give it more throttle then suddenly it grabs and jerks and takes off abruptly until I let off the throttle. One time I got in and pulled it into D and gave it gas and nothing happened at all, it was completely in neutral with the engine free revving under throttle even though the dash indicator showed D. I put it back in P then back to D and it went normally.

Other than those two oddball issues, my trans seems okay. I would still like to change the fluid just as a preventative measure, even if that means I have to pay for it and do it myself.

I did inquire at the dealer about the possibility of evaluating it for a fluid flush for the known issues, and the service writer told me something like "we cant do anything, gm isnt sending us any fluid until spring" which sounded like BS.

It may depend on where you live, I heard they were releasing it regionally. South Eastern are first?? I know we have it here (Florida Panhandle) because I know the service manager...odd thing is (and there are a ton of K2 GM trucks around here) they’ve done 2 yes 2 trucks since end of January. He said that yes, he is aware of the TSB/issue but that it isn’t on every single truck. Since he’s been there (going on 3 years) they’ve had 1 truck that they just never could get right and after several attempts THEY offered to buy it back, it didn’t have to come to any legal battle, they just did it right. I personally haven’t had any problems on my 8 speed but until yesterday I’ve driven mostly in L7 to avoid AFM. Bought a Range AFM disabler so now I can use Drive...keep ya posted ?

bigman32hockey · February 10, 2019

Has anyone here been able to fix the hard shift from 1st to 2nd under light acceleration? Or is this just the way it is with this transmission?

DeePa · February 10, 2019

Have you tried to disable grade braking?

push and hold tow haul button for 6 sec then release?

just a thought.

ajensen383 · February 11, 2019

On ‎2‎/‎8‎/‎2019 at 12:44 AM, hypntyz said:

I have an 18 sierra denali 6.2 bought new in march with 6800 miles on it now, and it seems like I'm one of the lucky ones without the shudder based on the descriptions I am reading here. I do distinctly feel the grab and release of AFM/V4 mode but otherwise it seems relatively smooth. There are very specific circumstances at low speed when the trans seems jerky. Such as if I'm rolling to a stop sign from say 20-30mph and I slow down to maybe 10-5mph but not completely stopped, then I apply throttle to pull out and accelerate again. The trans jerks and its as though it isn't sure what gear to be in for a couple of seconds.

Also I park at the bottom of my driveway so every time I get in to leave I have to climb a bit of a hill, a couple of times it is like the trans is in neutral until I give it more throttle then suddenly it grabs and jerks and takes off abruptly until I let off the throttle. One time I got in and pulled it into D and gave it gas and nothing happened at all, it was completely in neutral with the engine free revving under throttle even though the dash indicator showed D. I put it back in P then back to D and it went normally.

Other than those two oddball issues, my trans seems okay. I would still like to change the fluid just as a preventative measure, even if that means I have to pay for it and do it myself.

I did inquire at the dealer about the possibility of evaluating it for a fluid flush for the known issues, and the service writer told me something like "we cant do anything, gm isnt sending us any fluid until spring" which sounded like BS.

Ok it makes me feel better that im not the only one who has this issue.... From the looks of it, it seems that those of us with the 18s seems to have this problem..

ajensen383 · February 11, 2019

On ‎2‎/‎7‎/‎2019 at 4:13 PM, paracutin said:

You described my 2018 6.2 8 speed 2 to 1 shift perfectly.
I have also noticed that when I remote start the truck then put the key in and turn it to the RUN position the truck twitches (jerks is too strong of a word) just a bit as if the TCC engages and disengages in about 1 second.

The 2 to 1 shift is annoying and can be modulated a bit by taking my foot off of the brake for a half second just before the truck stops then reapply the brake. Seems to avoid the "neutral" feeling.

Mine will do the twitch on occasion, it doesn't happen all the time, but it did happen a few times already. Since its been cold here in the NE I have been remote starting daily and 8 times out of 10 I don't get the twitch but it does happen.... I also have been noticing from a cold start when I get in and put it in reverse sometimes it will shutter for a second then go into reverse.. It only seems to do this when its cold out or on a cold start.. Once its warmed up it seems ok... I still do not have any shutter or vibration yet with mine..almost 8700 miles

TRKLGND · February 11, 2019

19 hours ago, DeePa said:

Have you tried to disable grade braking?

push and hold tow haul button for 6 sec then release?

just a thought.

Disabling grade braking does nothing for me.

ajensen383 · February 11, 2019

One new thing that happened over the weekend...This only happened once so im not sure if it will be an on going issue... Driving home on the highway, pulling a light grade in 8th gear.. I went to pass a truck so I gave it some gas. Usually It will downshift into 7th and then when I let up it will go back to happily chewing along in 8th...This time it felt strange in the downshift, not even sure how to explain it, like it was caught in between gears and wasn't a firm downshift as usual, almost soggy feeling . It would not shift into 8th not matter what until I crested the grade. I tried going almost 80 and letting off slowly to make it shift, I tried manually putting it in 8th, nothing would get it to shift... After I crested the grade it was fine after that but wondering if it will happen again...

ajensen383 · February 11, 2019

7 minutes ago, paracutin said:

Disabling grade braking does nothing for me.

I tried this as well...nothing

I did try manually shifting down into 1st when coming to a stop, and that seems to eliminate it, but its a pain to do all the time

TRKLGND · February 11, 2019

53 minutes ago, ajensen383 said:

I tried this as well...nothing

I did try manually shifting down into 1st when coming to a stop, and that seems to eliminate it, but its a pain to do all the time

I agree with that. I find it inconvenient to shift into L (old manual mode) to keep the truck in 8 cylinder mode.