Possible Trans or TCC Issue

Jake707 · Aug 7, 2024

Our new to us 2017 yukon XL denali with 6.2 8 speed (173K miles) has what I originally thought to be possible sputter/misfire issues recently so I started with the basics. Changed spark plugs and wires (cylinder 8 is a real B*tch FYI), removed and cleaned the throttle body and added a catch can after seeing the amount of oil build up in the throttle body. I also added the Superior Solutions STL010 transmission bypass kit (basically the "Flip the Pill" project). None of this seemed to help much, if anything it feels like the problem might have got worse. After reading threads Im wondering if the problem Im having is transmission/TCC related.

While driving especially with mild acceleration, you can feel an almost sputter/slip/stutter and almost see the RPMs go up and down a 100 or so RPMs. Im finding it difficult to describe in text haha so hopefully this makes sense. My wife made the joke of it almost has to take two steps forward then 1/2 step back as it speeds up.

Does this sound like a transmission and/or TCC issue?

We have a full warranty plan we bought from the dealership with the car, would this generally be covered? If I bring it to the dealership to diagnose and/or work on, should I remove the trans cooler line bypass and re install the original "pill" assembly as it came? Im paranoid they might find that and void any warranty work?

Geotrash · Aug 7, 2024

Jake707 said:
Our new to us 2017 yukon XL denali with 6.2 8 speed (173K miles) has what I originally thought to be possible sputter/misfire issues recently so I started with the basics. Changed spark plugs and wires (cylinder 8 is a real B*tch FYI), removed and cleaned the throttle body and added a catch can after seeing the amount of oil build up in the throttle body. I also added the Superior Solutions STL010 transmission bypass kit (basically the "Flip the Pill" project). None of this seemed to help much, if anything it feels like the problem might have got worse. After reading threads Im wondering if the problem Im having is transmission/TCC related.

While driving especially with mild acceleration, you can feel an almost sputter/slip/stutter and almost see the RPMs go up and down a 100 or so RPMs. Im finding it difficult to describe in text haha so hopefully this makes sense. My wife made the joke of it almost has to take two steps forward then 1/2 step back as it speeds up.

Does this sound like a transmission and/or TCC issue?

We have a full warranty plan we bought from the dealership with the car, would this generally be covered? If I bring it to the dealership to diagnose and/or work on, should I remove the trans cooler line bypass and re install the original "pill" assembly as it came? Im paranoid they might find that and void any warranty work?

Common issue that's usually fixed with a transmission fluid change and a special additive. Search for transmission shudder in here for the details.

tom3 · Aug 7, 2024

I'd guess you'll have a complete failure soon. Same thing wth my son's Sierra. We thought it was a tank of bad gas. I would probably replace that thermostat valve pretty quick. You could drop the trans. pan and look at what's laying on the bottom - but with the warranty I'd just run it.

Jake707 · Aug 8, 2024

Geotrash said:
Common issue that's usually fixed with a transmission fluid change and a special additive. Search for transmission shudder in here for the details.

After reading this thread, it sounds like I should see if my local dealership can flush all fluids and put the new stuff in (Mobil 1 Synthetic LV ATF HP). Im assuming I would still want to add some of that lubegaurd Ive seen mentioned?

Shudder No More!

SHUDDER NO MORE! Hello gang, I’ll be damn so this fall our 2016 Yukon Denali with the 6.2. The transmission had started to shudder & I thought it was the AFM, so I had the AFM cancelled just to find out that the shudder was worst and may needed a torque converter. So I went to the dealership...

www.tahoeyukonforum.com

GM_Josho · Aug 8, 2024

Last year I recently experienced the same exact thing! I changed the fluid and it did not fix my issue. However, I did find a fair amount of shavings in the trans pan. I talked with a local transmission shop and was advised to replace the torque converter. I ended up making friends with the transmission tech there and we tore the transmission completely down, cleaned and reassembled it, as he didn't see anything worth replacing. I tuned out the transmission slip and got rid of the AFM. I've put over 10k miles on it since and have had zero issues!

Jake707 · Aug 9, 2024

Ended up dropping it off at the dealership this AM. If they pull the pan and nothing out of the norm is there then theyll do the full flush and new fluid. If they do find problems.................. well lets just hope I dont get that call today, although thinking about it, the warranty deductible for a new trans would probably be less than the fluid flush haha

Jake707 · Aug 9, 2024

Dealership sent this to me. They said the fluid was dark and had a slight amount of metal in the pan but was “normal” and didn’t give them red flags that the trans or TCC was going out. They are flushing now.

They did also say I need a full 4x4 service with fluid changes and that my rear shocks were blown but I’ll look at doing those myself lol

GM_Josho · Aug 13, 2024

Jake707 said:
Dealership sent this to me. They said the fluid was dark and had a slight amount of metal in the pan but was “normal” and didn’t give them red flags that the trans or TCC was going out. They are flushing now.

They did also say I need a full 4x4 service with fluid changes and that my rear shocks were blown but I’ll look at doing those myself lol

I agree. The fluid looks dark for sure. From what I can see the magnet doesn't look bad at all. You could change your shocks yourself, even with little mechanical skills. Once you get your vehicle back, watch your transmission temp gauge. I don't recall exactly what normal is, but I believe anything over 200 could indicate issues. Sounds like you may have caught it in time though!

Jake707 · Aug 13, 2024

We’ve been driving it for a few days now and haven’t felt the issue come back after the flush. I’m still trying to research if I should still add a bottle of that LubeGuard product to the trans or if the new fluid type is sufficient.

For the shocks I was starting to go down the rabbit hole of OE or aftermarket because of the huge price difference but my wife had the good idea of contacting the third party warranty company and seeing if they would be covered. Waiting on the call back from the dealership who has to work with them directly for confirmation but if covered I’ll gladly have them install the OE ones.

GM_Josho · Aug 14, 2024

Jake707 said:
We’ve been driving it for a few days now and haven’t felt the issue come back after the flush. I’m still trying to research if I should still add a bottle of that LubeGuard product to the trans or if the new fluid type is sufficient.

For the shocks I was starting to go down the rabbit hole of OE or aftermarket because of the huge price difference but my wife had the good idea of contacting the third party warranty company and seeing if they would be covered. Waiting on the call back from the dealership who has to work with them directly for confirmation but if covered I’ll gladly have them install the OE ones.

I second this decision as well! Its hard to say what some of those warranties will and wont cover. Best of luck!

Possible Trans or TCC Issue

Jake707

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Geotrash

Dave

tom3

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Jake707

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Shudder No More!

GM_Josho

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Jake707

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Jake707

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GM_Josho

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Jake707

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GM_Josho

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