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6L80 Trans HELP NEEDED PLEASE- re: TCC shudder and accidental use of 1 gal DEX III ATF during flush

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Charleston, WV
Hello all, hope everyone is healthy and has a Merry Christmas and Happy New Year!

Six years ago tomorrow I purchased a white 2011 LTZ 4x4 w/32k miles on it. Over the last 71.5 months I've put 107k miles on my Av and couldn't have been much happier with it! I've done really well with my required/recommended maintenance with exception of one fluid. I didn't change the fluid in my 6L80 Transmission at 100k like I was supposed to. My truck currently has 139k on the odometer.
On 11-9-20 I purchased 4 gallons of Valvoline Full Syn Dex VI ATF online from Advance Auto(or so I thought) in order to do a trans flush. When you purchase online they ask that you show up and call and they bring your items out. I followed their anti-virus protocol and opened my tailgate and they set four blue gallons in the bed along with the rest of my items. About two days later while just starting up a slight incline after a long (for WV) straight stretch at about 45mph with the truck in 6th gear I felt a vibration that I'm fairly positive is torque converter shudder, very similar to hitting the rumble strips on the side of the interstate at the same speed. This continued almost every time those conditions were re-created for the next 10-12 days. That was the first chance I had to change the fluid. It took me several days to figure out what was happening and I only drove a few hundred miles after the problem surfaced.
On 11-23-20 I did the trans fluid flush by disconnecting the line at the exit of trans cooler, attaching a clear hose that ran to a bucket and starting engine until I saw the first air bubble, which drained about 2.5qts and allowed me to get the pan off w/o drowning myself in fluid. The fluid was black, but there was nothing larger than shavings of metal on my magnet and not even an excessive amount. After re-torquing the valve body bolts, cleaning up pan, changing seal/filter, and putting pan back on I added 1 gallon of fluid through the fill tube and started engine. I kept adding new fluid as the old came out until it was running out clean. At that point I topped off fluid to hot level and went for a short drive. The TCC shudder was still there, although less violent than before.
Over the last 2 weeks Ive only driven it about 50 miles and Ive read about 55 miles of print about torque converters going out, transmission failing, TCC shudder fixes, etc.. Yesterday I drove it about 3 miles to get to temps and two torque converter tests I read about online. The test was to see if TC is still working correctly. It consisted of two throttle punches while in Park and an immediate step on the brake and shift into D while the RPM's are falling, which should send the TC into hyperdrive if it's working or send me through the back wall of my garage if not. It worked perfectly. I then checked fluid level again and it was just a little high, so I put a small diameter hose in the fill tube and drew a water bottle of fluid out to lower the level. It was black again already, or close to it. That made me think the fluid that was in the TC and whatever the new fluid had dislodged must've been really bad? so I decided to do another full flush and to add 4oz of LubeGard shudder fix at the end this time. Back to Advance Auto.com again for 4 more gallons, brake cleaner, and LubeGard.... and $156 later I was opening tailgate(of my buddies truck) and standing back like a good anti-virus customer should. Once home I started the tedious task of raising and leveling truck again. While aligning 6x6's as a backup to my jackstands I noticed the different labels on the blue jugs. One of them was Dex/Merc containing Dexron III, the cursing began. During my tirade it hit me "what if that happened last time? I don't think I even checked!" I went to the back of my garage where the jugs from the last flush were and sure enough 1 of the 4 was Dex/Merc Dexron III.... I'm not sure which order I put them in either, if it was the first obviously it's not as bad, however I'm going to guess based on the order they were sitting in that it was second to last.
Sorry for being so long winded, but I wanted to give a good backstory and snapshot of where I'm at... Thank you to whoever can offer some guidance in advance, Sincerely Dan

My questions are:

1. How bad is it that I ran approx 55mi with some percentage of Dex III in a 6L80?
2. Will another flush, which will be 5 gal this time get it out? or am I cooked?
3. Will the LubeGard Shudder fix potentilally help the TCC shudder?
4. How do I handle Advance Auto? Receipts both have qty: 4 Dexron VI 1gal, I should've caught it but I didn't. They have a "no liability" policy against employee negligence regarding products, but twice to me is more Gross Negligence? Should I only ask for the two gallons of Dex VI and a new filter?

I'm worried I've lost my transmission two weeks before making my last payment
 
Wow. I wish you well Dan. Good luck too!

1. Dex 6 is backwards compatible to Dex 3, so at least it won't sludge up or react negatively with each other. Whether the 6l80 can tolerate an unknown percentage of Dex 3 is another question altogether, but I'd venture to guess it did no harm for such short miles if the majority of the fluid was proper Dex 6.
2. Probably fine, but one way to find out!
3. Maybe, but I doubt it. Fluid changes should not improve things, it should be to simply maintain.
4. Go in and explain. Start off nice. I think they'd be understanding. Ask them to check inventory if they give you grief, they're hopefully off by exactly what they misgave you.

Good luck again man.
 
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Maybe the service manual can be of assistance. See attached
 

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  • auto transmission service.pdf
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Wow. I wish you well Dan. Good luck too!

1. Dex 6 is backwards compatible to Dex 3, so at least it won't sludge up or react negatively with each other. Whether the 6l80 can tolerate an unknown percentage of Dex 3 is another question altogether, but I'd venture to guess it did no harm for such short miles if the majority of the fluid was proper Dex 6.
2. Probably fine, but one way to find out!
3. Maybe, but I doubt it. Fluid changes should not improve things, it should be to simply maintain.
4. Go in and explain. Start off nice. I think they'd be understanding. Ask them to check inventory if they give you grief, they're hopefully off by exactly what they misgave you.

Good luck again man.

-Thank you for the empathy lol
-Advance was about a 15min call- Amber answered the phone was the manager and had no problem agreeing to exchange one full and one empty gallon of Dex III for VI and agreeing to giving me another filter, which had to be delivered from another store. Hoping I don't need to discuss anything else regarding this with them from here on...🤞
-I spent about 30min on phone with Valvoline Product Tech yesterday, prognosis: Good= stated VI is very compatible with III, that 50ish miles was not enough to worry about, and that III had some of the best detergent properties ever. The detergent aspect crossed my "glass half full" mind as I was pumping that blackish fluid up out of there also. He stated the LubeGard wouldn't hurt but likely wasn't necessary because their Dex VI was that advanced. He also recommended I call GM Tech for their opinion. **my thoughts= A+ Company Service, Product knowledge and application... BainMan do you work for Valvoline??
-Spent about 20min getting to a GM Technical Support Specialist and 20min discussing situation, prognosis: Good for tranny fluid flub but unsure regarding shudder.....and he had a valid point that I've also considered......it could still be something else.....w/o an oscilloscope to know the frequency and intensity of the vibration it could be motor mounts, u joints, transmission and or transfer case mounts, steering system related, misfire, etc. He recommended that I let him transfer me to my local Chevy dealer.
-Spent another 20min on phone with Technician and a Service Adviser from local dealer, prognosis: Fluid issue should be fine after another flush, did not recommend the LubeGard additive or any additive and of course welcomed me to bring it in lol...

-Just got this 6300lb machine up and level. Four HD jackstands backed up with three 6x6 4x6 and plywood jenga stacks in rear and one double wide stack in the front, lowest clearance is 23"; which is crucial for 6' 224lb dude to flop around like a killer whale on the beach under there. About to start a 5 gallon flush now.
-Lastly, man I''ve spent 17 days piecing together about 1/4 of what that auto transmission service manual has in it... THANK YOU VERY MUCH! One of my best friends has a body shop about an hour away on the OH WV border and he's bringing his Snap-On Ethos Pro over this weekend(if necessary) to see how many of these diagnostic functions we can perform... I'll let you know how it goes down.. Thanks again
 
-Advance was about a 15min call- Amber answered the phone was the manager and had no problem agreeing to exchange one full and one empty gallon of Dex III for VI and agreeing to giving me another filter, which had to be delivered from another store. Hoping I don't need to discuss anything else regarding this with them from here on...🤞
Glad that went well, the Advance Auto near me is great to work with as well. Sucks that you went through this ordeal though.
BainMan do you work for Valvoline??
Haha nope, I've just done some light reading on Dex VI.

-Spent about 20min getting to a GM Technical Support Specialist and 20min discussing situation, prognosis: Good for tranny fluid flub but unsure regarding shudder.....and he had a valid point that I've also considered......it could still be something else.....w/o an oscilloscope to know the frequency and intensity of the vibration it could be motor mounts, u joints, transmission and or transfer case mounts, steering system related, misfire, etc. He recommended that I let him transfer me to my local Chevy dealer.
I hope it is something more simple than the transmission! Bummer that it is yet to be diagnosed, sometimes that's the hardest part for me.

-Lastly, man I''ve spent 17 days piecing together about 1/4 of what that auto transmission service manual has in it... THANK YOU VERY MUCH! One of my best friends has a body shop about an hour away on the OH WV border and he's bringing his Snap-On Ethos Pro over this weekend(if necessary) to see how many of these diagnostic functions we can perform... I'll let you know how it goes down.. Thanks again
Glad to help. The factory service manual is a great resource. It has repair steps, circuit diagrams, troubleshooting steps, connector pinouts and basically everything a dealership tech would need besides tools or a tech2 in it. I think I got mine here from here ebay link
but if you need something specific or a few things PM your email address
 
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Glad that went well, the Advance Auto near me is great to work with as well. Sucks that you went through this ordeal though.

Haha nope, I've just done some light reading on Dex VI.


I hope it is something more simple than the transmission! Bummer that it is yet to be diagnosed, sometimes that's the hardest part for me.


Glad to help. The factory service manual is a great resource. It has repair steps, circuit diagrams, troubleshooting steps, connector pinouts and basically everything a dealership tech would need besides tools or a tech2 in it. I think I got mine here from here ebay link
but if you need something specific or a few things PM your email address

Just wanted to give you an update... (and get myself one step closer to posting the pics you requested lol)

-During my flush, while going through the procedures I found that the get the torque converter moving and ensure a total exchange of old for new fluid; my hose came out of the trans cooler and proceeded to saturate EVERY SINGLE SQUARE INCH of my engine compartment and put about 1.5 gal under my truck lol......and as dumb as that feels to type "lol" at the end of that compound sentence, that's all I could do. laugh and shake my head. Lesson learned= put a small hose clamp tight enough to hold its place on the hose and clamp it to the radiator. I spent the better part of two days cleaning up the mess. It was pooled almost 2" deep in the bottom of the fan shroud. I'd say half that time was spent on the intake and valve cover area. The smoke still rolled off the manifolds throughout the fluid warming process and was still trickling after the first test drive.... At least it wasn't brake fluid right!
-Taken two test drives so far, maybe 4 miles and the shudder is still there.. It seems a little less violent but..... I've got a Creader professional here beside me, bout to go back to work. ttys, Dan
 
Glad that went well, the Advance Auto near me is great to work with as well. Sucks that you went through this ordeal though.

Haha nope, I've just done some light reading on Dex VI.


I hope it is something more simple than the transmission! Bummer that it is yet to be diagnosed, sometimes that's the hardest part for me.


Glad to help. The factory service manual is a great resource. It has repair steps, circuit diagrams, troubleshooting steps, connector pinouts and basically everything a dealership tech would need besides tools or a tech2 in it. I think I got mine here from here ebay link
but if you need something specific or a few things PM your email address
Wanted to follow up with closure. After borrowing my buddies Snap-On ETHOS and telling the computer that I'd changed the tranny fluid and running every other kind of test I could run with that thing... The truck ran like a champ and shifted perfectly with and without a trailer all over the WV mountains this winter..............until.............and that's gonna be a new thread I guess. GOnna go research for others who about it in hopes of finding my answers through research instead of just asking someone... It's regarding Rich conditions in both banks, and intermittent misfire in cylinder #7 and an intermittent lifter collapse tick in 3-5-or 7??... Thank everyone for your help and if I come up with any tricks for this one I'll post them under that subject
 
Wanted to follow up with closure. After borrowing my buddies Snap-On ETHOS and telling the computer that I'd changed the tranny fluid and running every other kind of test I could run with that thing... The truck ran like a champ and shifted perfectly with and without a trailer all over the WV mountains this winter..............until.............and that's gonna be a new thread I guess. GOnna go research for others who about it in hopes of finding my answers through research instead of just asking someone... It's regarding Rich conditions in both banks, and intermittent misfire in cylinder #7 and an intermittent lifter collapse tick in 3-5-or 7??... Thank everyone for your help and if I come up with any tricks for this one I'll post them under that subject
Let me know what your did on scanner
 
It's been a few months and I've been wrestling with my -lifter, miss, rough idle, sensor, valve cover, etc?- issue for the last month+. During that stretch I've also used two different scanners so forgive me for being foggy minded. To the best of my memory on the Snap-on Ethos I ran checks on the injectors which may or may not have helped; and I told the truck that I had replaced the transmission fluid. I stopped short of a total reset of the trans control unit because (to best of my research) you should only do that if you replace parts. Hope that helps.. Let me know if you have anymore questions

In hindsight I wish I would've bought an oscilloscope to attach to my seat track and record the vibration frequency, could've used it to diagnose what I'm wrestling now. Eventually I found a site with GM diagnostics info that could confirm if the vibration was a wheel bearing, a transmission, a lifter, tires etc based on the size and timing of the wave the vibration creates. Would've helped me with all the second guessing of myself lol
 
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