I'm about 7 months out. It had that "caddy" ride for about a month but back to factory normal now. Sometimes clunky shifts, etc but what I would expect from a truck transmission so no complaints. I noticed AFM stays engaged more even under slight pedal press so they modified the sensitivity on that with new programming so it has a slight vibration at even lower RPMs like 1100 if you have some slight acceleration which is what I think they were trying to avoid with the TCC pulsation to begin with.
I'll give it a go but wouldn't you expect it to vibrate regardless of braking if it were unbalanced due to bent rim or rocks? My issue is only while braking at 60+ MPH. I do know I have some rocks in it but not that much. Continental tires on my (OE) although they were replaced at 10K due to a recall. I get mine balanced and rotated every oil change and have seen the balance weights on it. Another thing I saw to check for is any play the wheel has.
Is there a service bulletin for the Chevy shake issue? Are you talking about the TCC vibration (light acceleration at 60+ MPH around 1200 RPM) combined sometimes with AFM? - If not, not familiar with the chevy shake.
2015 GMC Yukon Denali - 32k miles (6.2L + 8spd). I don't normally do highway speed but noticed yesterday that I had a slight pedal vibration when doing so and it only seems to happen at 60+ mph. My daily drive is under 40mph and no vibrations there. I'm assuming its likely a rear rotor since I don't feel it in the steering wheel. I looked back on my records and it appears front brakes were at 7mm a year ago and rear at 4mm. Both in the "green" according to dealer. I'm not sure if its an eyeball check and they just mark good or if they actually measure but it was 10k miles ago and a year so I likely need new pads. All this to say, with this life and mileage is anyone seeing pad life and possibly rotor life exhausted so quickly? This is a heavy vehicle and the 6.2L gets it up to speed quickly and it does seem to take a lot more to stop it(always this way so I don't think its the vacuum recall). If anyone is getting a 4 wheel brake job at the dealer, what has it run you? Mine is running a special for $139 per axle for pads and $189 per axle for rotors but I'm hoping if it is a warped rotor I only need 1 pair. Also noticed this on the front passenger rotor. Is that defined of a groove normal? To the touch it doesn't feel grooved. Tire inflation is normal.
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.
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.
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.
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.
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.
Its an issue specifically with the 8L90 (8 speed) 2015-2017 and possibly 2018 too so it affects a ton of GM vehicles. Due to the wide impact I am sure they really want to fix this and this might finally be the permanent one. Mine is actually a Yukon though. Or they may just start phasing in the 10L90 to replace it but I hear that has some similar problems. Mine is a 2015 and I just hit 31k miles. My normal driving though doesn't typically lend to reproducing the issue. Most of mine is 40mph back road driving and when I'm on the highway its short enough to be regular acceleration up to highway speed and then pretty quickly slowing down to exit. If you're on the highway a lot and cruising, you're more likely to run into this a lot. I occasionally had the surge but that's very rare, could be grade baking and you can turn that off by holding the tow button for 5 seconds. If you're at a point where they will actually take it back, could be your best bet because if you do the flush and it comes back a year later you will have substantially less leverage to turn it back in.
I'm 3 weeks out from my flush and its perfect. The delayed garage shifts are gone, no clunking and shudder completely gone, haven't had a rough shift since but time will tell for sure because I've done this before and the torque converter replacement and flush I did last time lasted 2 years. They claim this is the "permanent" fix but there's no telling if that will be the case. For me, if I have to flush it every 2 years I'd probably just deal with that and pay for it myself if I had to because I like everything else about the truck.
Yes, with the brand new fluid flush it's been flawless for the past couple of weeks. Even the clunky shifts, delayed garage shifts and sometimes generally rough shifts are gone but this also happened 2 years ago after the TC replacement so time will tell. As I understand it its an accumulation of moisture in the fluid that causes the issues and it builds up over time, particularly in high humidity areas.
For me, I did my first flush about 2 years ago and it lasted a month or two. They then did the TC replacement and flush and it seemed to last until about 2 months ago. Talking to the service advisor they have been through at least 3 different fluids for this.
I just realized I had not updated this post with the information on the new procedure. There are a couple other forums that I was posting on. The new procedure is 18-NA-355 which includes a new tool used to flush/fill and a new fluid. Its the new fluid that is supposed to be a permanent fix. Part number on the fluid is 19417577. After a day driving in various conditions the transmissions is still very responsive. This is supposed to be the final fix but only time will tell as this issue does not immediately reappear.
Most OnlineNewest Member
Who's Online 155 Members, 1 Anonymous, 2,424 Guests (See full list)
- Will Tarkington
- Kyle Wess
- Brian Burdick
- Retired Bob
- Bobby Bouchee
- Juan Segura
- Dock Rocker
- Cory Hawk
- Booger T
- Henry Martinez
- michael betz
- Williamzivkovich i
- Big Sky Eric
- Miguel De Dios