214K 6L80 rebuild before TCC failure

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MWD_CTSV

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My new to me 214K mile 2011 Yukon Denali XL had brown transmission fluid, and it seemed like I was on borrowed time after reading lots of info on this forum. It shifted fine, but I figure now is the time to investigate and be proactive, so I pulled the trans.

I recommend pre-emptively replacing the torque converter at 150K miles if everything is stock including DOD/AFM, tune, etc. Changing the TCC engagement and DOD/AFM may help prolong the life, and if you are the owner from low miles with extensive fluid/filter service, maybe this doesn't apply. If you have a 2010+ 6L80 with no shifting issues or cracked/leaking drums, and good maintenance you may be one of the lucky ones that could go 300K+ with just a new converter and valve body updates without a true rebuild.

If you watch the rebuild or disassembly videos on youtube, you definitely see the carnage from the common TCC failure destroying the pump and sending metal everywhere causing all sorts of issues. I don't know how close I was to TCC failure, but I wanted to give a little insight as to what a high mileage trans looks like without a TCC failure. My filter was dated 2011, so it is original. I have no idea of the service history of the trans, but the fluid was pretty brown, but not burnt smelling or tar like. 4-5-6 clutches were slightly worn, but none of the piston seals were damaged.

bellhousing_pump.jpg

I did replace the bellhousing because it was only $120 for the new GM part with a new bushing and seal, but the original is reusable. I only did some brief scotchbrite cleaning to verify the scratches were minor.

pump_stator.jpg

I did reuse the pump stator, and you can see here the pump surface is super clean. 2011 already has the updated seals, so no reason to upgrade. I did do the Sonnax zip kit which supplies an upgraded pressure regular valve, but mine was undamaged unlike many others (which I think is related to metal from clutch failure).

The only real issue for my less-than-proper-serviced trans was a seal between the case and valve body, which could have been replaced with the trans in the vehicle. So I feel pretty confident that replacing the torque converter and servicing the valve body will greatly extend the life of a 6L80. And you can do both of these without moving the trans outside the frame rails.
 

swathdiver

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Just dropped the pan in mine for the first time and changed the filter at 184K. It was not as dirty as I expected. Still running strong. Fluid has been changed 3 times.

I bet that fluid in yours was original. Do you have a bi-directional scan tool to run the Fast Learn Adapts when you get it back together? Also, there is an internal transmission oil life monitor that you can view and reset.
 
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My new to me 214K mile 2011 Yukon Denali XL had brown transmission fluid, and it seemed like I was on borrowed time after reading lots of info on this forum. It shifted fine, but I figure now is the time to investigate and be proactive, so I pulled the trans.

I recommend pre-emptively replacing the torque converter at 150K miles if everything is stock including DOD/AFM, tune, etc. Changing the TCC engagement and DOD/AFM may help prolong the life, and if you are the owner from low miles with extensive fluid/filter service, maybe this doesn't apply. If you have a 2010+ 6L80 with no shifting issues or cracked/leaking drums, and good maintenance you may be one of the lucky ones that could go 300K+ with just a new converter and valve body updates without a true rebuild.

If you watch the rebuild or disassembly videos on youtube, you definitely see the carnage from the common TCC failure destroying the pump and sending metal everywhere causing all sorts of issues. I don't know how close I was to TCC failure, but I wanted to give a little insight as to what a high mileage trans looks like without a TCC failure. My filter was dated 2011, so it is original. I have no idea of the service history of the trans, but the fluid was pretty brown, but not burnt smelling or tar like. 4-5-6 clutches were slightly worn, but none of the piston seals were damaged.



I did replace the bellhousing because it was only $120 for the new GM part with a new bushing and seal, but the original is reusable.
Definitely agree with replacing the converter at 125k or so regardless of whether its working well or not as they are ticking time bombs…Did you upgrade the converter clutch to the thicker version’s available (.045 or .066) and have a billet cover installed?

Here’s some info on those JMBX converters:

 
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MWD_CTSV

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Just dropped the pan in mine for the first time and changed the filter at 184K. It was not as dirty as I expected. Still running strong. Fluid has been changed 3 times.

I bet that fluid in yours was original. Do you have a bi-directional scan tool to run the Fast Learn Adapts when you get it back together? Also, there is an internal transmission oil life monitor that you can view and reset.
Thanks for the heads up on the trans oil life monitor! I didn't know that existed.
Honestly, I didn't do any diagnostics on the trans yet. I have an Autel and a Tech2, and I'm pretty sure the Tech2 can do the relearn.
 

swathdiver

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Funny, I just read that article this morning!
Thanks for the heads up on the trans oil life monitor! I didn't know that existed.
Honestly, I didn't do any diagnostics on the trans yet. I have an Autel and a Tech2, and I'm pretty sure the Tech2 can do the relearn.
Yep, Tech-2 can do it.
 
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MWD_CTSV

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Definitely agree with replacing the converter at 125k or so regardless of whether its working well or not as they are ticking time bombs…Did you upgrade the converter clutch to the thicker version’s available (.045 or .066) and have a billet cover installed?

I went with the billet cover CVC BU60FHD that was recommended here. A friend offered a CTS-V converter, but I still chose the CVC. I also did a new pump, slide and spring along with the Sonnax zip kit, which includes several items to help with pump pressure regulation and the TCC specific one, that is recommended by the rebuilder (CVC) to help the life of the TCC.
 

RobH

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It's possible that the OP's transmission had had some fluid flushes without getting into the pan to replace the filter. Never the less, replacing the converter is a good idea.

After mine went south after 123K miles, taking the tranny with it, I think that I would suggest replacing the converter at 100K miles. And put in a quality upgraded converter. My 2016 Tahoe had 80K miles when I bought it. I drove the Tahoe taking it easy to make the engine and transmission last. Normally, on the highway, I cruise at 65. When pulling my 3200 pound Casita, I cruise at 60 MPH in fifth gear. I have the 3.42 rear axle which should make life easier on the engine and tranny.

I changed the fluid and filter at 90K miles. I did not know about the service bulletin to replace the 90 Centigrade transmission Thermal Bypass Valve with a 70 Centigrade valve. If I had known, my trannsmission might have held up. I'll be doing every other year fluid replacement on my remanufactured transmission. If I still have it at 100,000 miles, I'll replace the converter.

t's possible that the OP's tranny had some work on it before he bought it. Or, it may be at the good end of the bell curve on lifespan to have lasted to 214K miles.
 

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skpyle

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I went with the billet cover CVC BU60FHD that was recommended here. A friend offered a CTS-V converter, but I still chose the CVC. I also did a new pump, slide and spring along with the Sonnax zip kit, which includes several items to help with pump pressure regulation and the TCC specific one, that is recommended by the rebuilder (CVC) to help the life of the TCC.
Hello MWD-CTSV!
How/where did you source the CVC converter? I have been having trouble finding one.

Thanks!
 
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I went with the billet cover CVC BU60FHD that was recommended here. A friend offered a CTS-V converter, but I still chose the CVC. I also did a new pump, slide and spring along with the Sonnax zip kit, which includes several items to help with pump pressure regulation and the TCC specific one, that is recommended by the rebuilder (CVC) to help the life of the TCC.
Good decision to install the zip kit…

For more context around 6L80 TC and related failures: The factory pump pressure regulator valve (pump cover) and TCC regulator valve (lower valve body) wears on the “balance spool” end of the valve allowing oil to bypass the valve sealing surface. This results in insufficient converter clutch pressure (in a nutshell) which, combined with the .020” converter clutch (way too thin), leads to premature converter failure. This is known to frequently happen inside of 100k.

All 6L80es should receive at minimum those two drop-in valves installed, along with the Sonnax boost valve, on overhaul to prevent recurrence of those issues. The Sonnax zip kit has all three and more…New converter should have a converter clutch that’s at least .045” thick (thicker=better).
 

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