16-NA-175 8 Speed Shudder UPDATE

[Jaychevy81]

 
Mine was flawless and perfect but I think the dealer went through half a tank of gas while they had it so they may have driven it a bit to go through a relearn if they did one.  I think the procedure usually calls for it.
 
Did your dealer cite 18-NA-355 or a different procedure?  18-NA-355 is the latest and the latest fluid is 19417577.
 
They claimed they put a new programming on mine.  Not sure what the programming was for but it seems to keep AFM engaged longer during times when a shudder would have normally happened.
 
They didn't indicate whether they did a relearn or not but I've had relearns done in the past and it was clunky for 100-200 miles afterwards.  They may not be able to tell you but did they do a relearn or fast relearn?
 
As I understand it, the constant learn and relearn is needed because the tolerances on the 8 speed (and probably 6 speed) are so tight that even two otherwise identical 8L90s could have slightly different pressures needed and over time these change so it is constantly learning.  They do a relearn so that it learns these all over again incase it has learned some "bad habits" during the shudder.

They did do the 18-355 and he said he did a fast relearn. it does seem diff then before I can say that. But still clunky when coming to a stop. It’s all the lower gears under 40mph. I will give it the 200 miles or so before I contact them. It’s a start anyway I love the truck Though no question there.


Sent from my iPhone using Tapatalk

[Jaychevy81]

Also I could be wrong but I feel AFM plays a part in it. I have AFM turned off. So I’m gonna give it time see how this goes. If not I will bring it in see what they say next. I may cut the flapper off the factory exhaust. Have it welded back on and Urn AFM back on then bring it to the dealer for a re learn but one step at a time.


Sent from my iPhone using Tapatalk

[dwchapmanjr]

1 minute ago, Jaychevy81 said:

Also I could be wrong but I feel AFM plays a part in it. I have AFM turned off. So I’m gonna give it time see how this goes. If not I will bring it in see what they say next. I may cut the flapper off the factory exhaust. Have it welded back on and Urn AFM back on then bring it to the dealer for a re learn but one step at a time.


Sent from my iPhone using Tapatalk

AFM absolutely can but for the TCC shudder it is isolated to the TCC.  Part of 18-NA-355 involves them reproducing the issue so that they can lock the TCC and unlock the TCC.  If they cannot reproduce with both of those, its a TCC/fluid issue.  The bulletin also states some parameters such as if it can't be reproduced with AFM disabled that it may likely be "normal" AFM shudder during engage and disengage which seems to happen a lot less after the programming they do in 18-NA-355.

 

My understanding is that the reason they have the 10 rpm slip at all in the 1200-16000 RPM range is the buffer vibration from AFM.

[Jaychevy81]

AFM absolutely can but for the TCC shudder it is isolated to the TCC.  Part of 18-NA-355 involves them reproducing the issue so that they can lock the TCC and unlock the TCC.  If they cannot reproduce with both of those, its a TCC/fluid issue.  The bulletin also states some parameters such as if it can't be reproduced with AFM disabled that it may likely be "normal" AFM shudder during engage and disengage which seems to happen a lot less after the programming they do in 18-NA-355.
 
My understanding is that the reason they have the 10 rpm slip at all in the 1200-16000 RPM range is the buffer vibration from AFM.

Which makes sense and I def can feel a diff in the shifts that I can tell. I know there will be weird shifts here or there totally understandable. Either way I love the truck it will work out the dealer is pretty cool as well.


Sent from my iPhone using Tapatalk

[dwchapmanjr]

3 minutes ago, Jaychevy81 said:

Which makes sense and I def can feel a diff in the shifts that I can tell. I know there will be weird shifts here or there totally understandable. Either way I love the truck it will work out the dealer is pretty cool as well.


Sent from my iPhone using Tapatalk

Having a good dealer that will work with you on this is key.  I had to take mine to a dealer other than the one I purchased it from to give this the proper attention.  If the clunky shifts don't go away I believe they may try one more flush and if it happens again replace the torque converter.  Depending on how long the shudder has been happening its entirely possible the TCC has some damage as the shudder is coming from the TCC.  As I understand it, there really is no way to partially engage to let it slip 10rpm so the shudder we feel is the pulsating of the TCC to fake being partially engaged.

 

[Jaychevy81]

Update so far I can tell a big diff last night and also this morning. It seems to have helped compared to when I dropped it off. No clunks or bangs no shudders as of now. Shifts are smooth and seems to be shifting when it should.


Sent from my iPhone using Tapatalk

[GPHusker]

I have about 850 miles on mine since the flush. Everything seems to be good. No shudder. The transmission shifts differently than it did before but in a good way. It shifts quickly and smooth. The only issue I have with any shifting is when the trans is very cold it sort of does a weird 1-2 shift the first time or two when you are slowly accelerating. I chalk that up to cold temps though. 

[Cjc]

I'm getting my done on Monday,I will let you know how it is.

[mattshiz]

hello everyone. I have a 2016 sierra with 66000 miles experiencing the same issues. I was going to schedule with the dealer to do the fixes but since I am out of warranty would it make more sense to have my local shop do it instead (cheaper, trust them more)? The dealer I bought the truck at is far away and will not cover the change. How much around will it cost me to do the transmission fluid flush through a GM dealer? I am hoping it is just the tranny flush and I will not need a new TC. Any info would be great! thanks guys!

[dwchapmanjr]

39 minutes ago, mattshiz said:

hello everyone. I have a 2016 sierra with 66000 miles experiencing the same issues. I was going to schedule with the dealer to do the fixes but since I am out of warranty would it make more sense to have my local shop do it instead (cheaper, trust them more)? The dealer I bought the truck at is far away and will not cover the change. How much around will it cost me to do the transmission fluid flush through a GM dealer? I am hoping it is just the tranny flush and I will not need a new TC. Any info would be great! thanks guys!

Not sure on price as all of mine have been no charge but I'd feel better taking it to a transmission shop first and seeing if they've done any before over a general repair shop.  Its a special fluid that only dealers may be able to get(maybe not) with a special procedure and tool kit.  It is also possible you may have to do this flush a couple of times to diagnose needing a new TC.  I want to say I saw the price of the new TC they put in mine and it was only about $350 but not sure what labor would be on top of that.

[Abiker21]

7 hours ago, mattshiz said:

hello everyone. I have a 2016 sierra with 66000 miles experiencing the same issues. I was going to schedule with the dealer to do the fixes but since I am out of warranty would it make more sense to have my local shop do it instead (cheaper, trust them more)? The dealer I bought the truck at is far away and will not cover the change. How much around will it cost me to do the transmission fluid flush through a GM dealer? I am hoping it is just the tranny flush and I will not need a new TC. Any info would be great! thanks guys!

Get a copy of the service bulletin and ask your local guy how close he can get to accomplishing it. Early on GM didn't realize the importance of flushing the cooling lines and were chasing their tails when the problem showed back up soon after.... it must be a bad TC....

[mattshiz]

I actually called up a buddy who works with chevy/gm who will have it done in their dealers shop and follow the TSB. I wasn't aware that cooling lines needed flushed also. I will ask him about this. They said it will run around 200-250$. Getting it done Thursday, hope it fixes the problem.

[mattshiz]

Got the TSB done today. Multi flush with the Mobil 1 fluid. Everything seemed to be resolved for the ride home. 

[dwchapmanjr]

1 minute ago, mattshiz said:

Got the TSB done today. Multi flush with the Mobil 1 fluid. Everything seemed to be resolved for the ride home. 

I'm about 5 months out without any issues although it took a year or two last time for it to crop up again.

 

What I have noticed it is shifted like brand new for about a month but back to the occasional clunky shifts (which is fine, its a truck).

 

The interesting thing is I notice with AFM on, I get a slight vibration when slightly riding the gas at low acceleration at about 200 rpm lower than the shudder.  What I think this is, is the shudder was them pulsating the TCC to avoid the V4 shudder and this is just the V4 shudder happening like you'd get with a stick shift 4 cylinder in too high of a gear to accelerate.  I'm not concerned about it because it doesn't feel like something is generating friction that is going to wear a part but it was an interesting observation.

[AdioSS]

Reading this thread gives me hope & pisses me off at the same time. My 18 Sierra developed the shudder early on. I took it to the dealer for the first oil change a couple hundred miles ago. They said I do have the shudder (duh), but they have several customers ahead of me “waiting on parts” & will contact me when they come in... 

 

It is just a thorough fluid flush, right?