Yet another yukon transmission thread...

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RogueAngel541

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Hello all,
Forum newbie here and hoping for some guidance. Sorry for the long post, but trying to relay as much info as possible. I am an ASE master tech, only I got out of the automotive world before so many electronics were integrated into every system they could muster. Only bringing that up to say that i do understand how things work to certain degree and that my way of thinking about the symptom may be a bit outdated. I recently purchased a 2016 yukon xl 5.3l as a family vehicle and I am running into an issue with the 3-4 shift in the transmission. Trans was rebuilt not long before we bought it. I have searched what seems endlessly and read many forums but haven't ran across anything yet that fully matches my issue. A few months after we purchased the truck, our first cold snap hit and took out the 3 year old battery. After I replaced the battery and reset the systems, the symptom started a day later. When driving it shifts fine in all gears except going from 3 to 4. Sometimes it just hits harder and other times it's like it shifts out of third, rpms spike for a moment and then kicks into 4th. Never happens on downshift or any other gear. Thinking that it needed a reset after the battery was replaced, I took it to a reputable trans shop in the area and they did a reset on the computer. It shifted perfectly when I left there. Three days later, the issue started again. As it was a day before leaving for our vacation, I had a buddy of mine with a scan tool reset it again. It shifted fine the entire vacation. Two days after we returned home (6 days total), the issue was back again. My sister inlaws boyfriend is a bit of a gm enthusiast so I gave him a call. Come to find out he has everything needed to reprogram/tune the trans but he was a bit stumped on the issue. He came by and downloaded the stock flash file and checked for codes. No codes are present so he attempted a solenoid clean out via the ecu (basically buzz the solenoids to push any trash out) then did another reset and fast relearn. Shifted perfectly for a few weeks this time but the issue has come back. I am wondering if anyone else has seen this issue before. I'm thinking solenoid pack and/or a tcm issue, maybe? Not really making sense to me as to why it would go away with a reset and then come back. I am still going to have him do the reflashing/tuning but should I try replacing the solenoid pack first beforehand since it will need to be programmed when replaced anyway? Hopefully someone out there has some insight on something I may be missing.
Thanks in advance
 

Marky Dissod

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Check the SPID in your glovebox for either of these RPO codes
MYC = 6L80E
MYD = 6L90E (Heavy Duty)

If neither of those is there, let us know which RPO code(s) you do have that start with M.
Maybe you have an 8L90E?

If you pushed any trash out of the solenoids, but did not change the ATF, where's the detritus now?
Before @NickTransmissions shows up, I'll tentatively suggest flushing out the old ATF and adding new ATF and filter.
(There is no such thing as fluid-for-life or any horseschidt like that.)
 
OP
OP
RogueAngel541

RogueAngel541

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Check the SPID in your glovebox for either of these RPO codes
MYC = 6L80E
MYD = 6L90E (Heavy Duty)

If neither of those is there, let us know which RPO code(s) you do have that start with M.
Maybe you have an 8L90E?

If you pushed any trash out of the solenoids, but did not change the ATF, where's the detritus now?
Before @NickTransmissions shows up, I'll tentatively suggest flushing out the old ATF and adding new ATF and filter.
(There is no such thing as fluid-for-life or any horseschidt like that.)
Good point. I assumed the filter would catch it. It's the 5.3 motor rwd so it should be the 6L80E, but I will verify by looking for the code.
 

Joseph Garcia

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Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum, and more will be coming from Nick.
 

NickTransmissions

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No problem, sorry about that. Thank you, from Texas

Paragraphs are a must as most folks consume these forums on a cell phone and your OP looks like a wall...that said, I think your 4-5-6 clutch may be wearing and clearance is now above spec so you're starting to see shift flaring. The TEHCM is adapting to the extent it can but there's only so much electronic compensation that can be done to "fix" a mechanical problem.

There's also a chance you could have an intermittent CPC solenid failure or valve body issue. I'd pull the TEHCM and valve body, bench test both then air check the 4-5-6 clutch and compensator feed circuit via the pump when the TEHCM / Valve body complex is out of the way. Also replace the VB-pump/center support seals as they can also be a source of drivability symptoms.
 

Jonmurphy

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Hello all,
Forum newbie here and hoping for some guidance. Sorry for the long post, but trying to relay as much info as possible. I am an ASE master tech, only I got out of the automotive world before so many electronics were integrated into every system they could muster. Only bringing that up to say that i do understand how things work to certain degree and that my way of thinking about the symptom may be a bit outdated. I recently purchased a 2016 yukon xl 5.3l as a family vehicle and I am running into an issue with the 3-4 shift in the transmission. Trans was rebuilt not long before we bought it. I have searched what seems endlessly and read many forums but haven't ran across anything yet that fully matches my issue. A few months after we purchased the truck, our first cold snap hit and took out the 3 year old battery. After I replaced the battery and reset the systems, the symptom started a day later. When driving it shifts fine in all gears except going from 3 to 4. Sometimes it just hits harder and other times it's like it shifts out of third, rpms spike for a moment and then kicks into 4th. Never happens on downshift or any other gear. Thinking that it needed a reset after the battery was replaced, I took it to a reputable trans shop in the area and they did a reset on the computer. It shifted perfectly when I left there. Three days later, the issue started again. As it was a day before leaving for our vacation, I had a buddy of mine with a scan tool reset it again. It shifted fine the entire vacation. Two days after we returned home (6 days total), the issue was back again. My sister inlaws boyfriend is a bit of a gm enthusiast so I gave him a call. Come to find out he has everything needed to reprogram/tune the trans but he was a bit stumped on the issue. He came by and downloaded the stock flash file and checked for codes. No codes are present so he attempted a solenoid clean out via the ecu (basically buzz the solenoids to push any trash out) then did another reset and fast relearn. Shifted perfectly for a few weeks this time but the issue has come back. I am wondering if anyone else has seen this issue before. I'm thinking solenoid pack and/or a tcm issue, maybe? Not really making sense to me as to why it would go away with a reset and then come back. I am still going to have him do the reflashing/tuning but should I try replacing the solenoid pack first beforehand since it will need to be programmed when replaced anyway? Hopefully someone out there has some insight on something I may be missing.
Thanks in advance
Hi It seems most likely there is trash in your fluids it's coming up I don't see any other explanation How can I shift perfectly Buzz the valve And it's good few days later it's not good. Have you done a trans flush through the cooler line ? And make sure you have a good filter. As I've said several times here I use a dual filter Can you use a car oil filter If you use this Mobile 1 filters they clean 110 micron filtering So when you run them in parallel, The floor is cut in half so you'll be able to filter it down to about 5 microns, for those who don't understand the filter media, Will filter much finer at a slower flow rate.
Murphy's law
 
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