214K 6L80 rebuild before TCC failure

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Geotrash

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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).
So, if I read this right, just replacing the converter with a beefier unit may not mean that we're in the clear unless we make those other mods. Do I have that right?

Also, I just chatted with my local transmission shop (Hyltons Transmission Service here in Mechanicsville, VA) and he said that he no longer installs the CVC converters because they were just bought out by another nationwide company that doesn't stand behind them the way CVC did. Still the same remanufacturing process though so he thinks they still build a great converter, but he just doesn't want to do business with them any more.
 
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So, if I read this right, just replacing the converter with a beefier unit may not mean that we're in the clear unless we make those other mods. Do I have that right?
Correct, @Geotrash. You have to address the hydraulic design weakness that contributes to TCC pattern failure as well as the converter clutch design flaw which also contributes to failure.

Majority of transmissions require numerous updates/upgrades to sufficiently address design or manufacturing flaws, 6L80e has quite a few…
 
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MWD_CTSV

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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).

Just to reiterate what Nick is saying in layman's terms is that the aftermarket (mainly Sonnax and Transgo) are providing alternates to the common problems both from wear and performance, based largely on common failures seen in the field. I was fortunate to not see any valve wear, but all the professional re-builders do, so they are keenly aware of the reality. Granted most pros are only rebuilding 'failed' transmissions, but the downhill curve of failure almost 99.9% traces back to some kind of clamping control failure.

Also with many examples of extended TCC life support via increased pressures and reduced slip targets (with TCM tuning), I think that also proves that pressure control is a key element. Of course it also possible for the regulator valves to fail in over-pressure which can also damage the TCC, especially in stock form.
 
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MWD_CTSV

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So, if I read this right, just replacing the converter with a beefier unit may not mean that we're in the clear unless we make those other mods. Do I have that right?

Also, I just chatted with my local transmission shop (Hyltons Transmission Service here in Mechanicsville, VA) and he said that he no longer installs the CVC converters because they were just bought out by another nationwide company that doesn't stand behind them the way CVC did. Still the same remanufacturing process though so he thinks they still build a great converter, but he just doesn't want to do business with them any more.

Yes, I would say that replacing the converter may not be enough. It does seem that some are honest enough to admit some shudder comeback problems even with new converters (and valve upgrades). Is it poor quality converter clutch material, poor resurfacing, or just reusing bad converter cores that should go in the junk pile? It is difficult to know because you would have to cut the weld to inspect the converter internals.

Just an update on my new CVC converter, I have had some issues with shudder after some long distance towing with the stock settings. Logging showed some pretty severe slip fluctuations, which I have been able to resolve with increasing the TCC pressure and reducing the desired slip. It may have been foolish to keep the stock settings, but the first 1000 miles were flawless other than some minor but noticeably harsh downshifts from 2-1 an maybe 3-2.
 
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Yes, I would say that replacing the converter may not be enough.
It’s definitely not enough just to replace the converter; the hydraulics have to be addressed or you’re simply restarting the count down to converter premature failure. Tuning also helps a great deal, as you pointed out.

Is it poor quality converter clutch material, poor resurfacing, or just reusing bad converter cores that should go in the junk pile?

Easy-Short answer? Yes to both; upon disassembly we see warped covers more often than not. You combine that with inadequate clutch design/spec and TCC regulator and control deficiencies along with less-than-optimal factory apply strategies, it’s a wonder that they last as long as they do.
 
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MWD_CTSV

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You combine that with inadequate clutch design/spec and TCC regulator and control deficiencies along with less-than-optimal factory apply strategies, it’s a wonder that they last as long as they do.
In hindsight, that is probably the understatement of the year. I was thinking all the mechanical improvement, regulation, better pressure, tight tolerances, stronger/straighter friction surfaces would help the computer to compensate less.

Because the computer guesses (I mean characterizes, haha) the actual pressures it could be doing things to create more hysteresis (fluctuation) instead of smoothing.

With the stock settings, the original red flag was a strong noisy shudder going up a steady incline in 5th at about 50mph and maybe a slight acceleration. It was the kind of drivetrain noise that makes you think u-joint failure because of the slight but rapid velocity changes in the driveshaft, resonating quite noticeably. I didn't actually log this condition, but it did present in a lesser form after some initial tuning, and it was quite evident that the measured TCC slip was yoyo-ing up and down rapidly. If I give the benefit of the doubt to the converter builder, such that the friction is good (lets say it mated nicely and has a good grip above a stock JBMX, and the TCC engagement quickly reduces slip such that the computer counters by reversing the pressure quickly causing a nasty slip/catch cycle which is shudder.

My current tune is to increase the TCC pressure (well below what others are using), bump the apply ramp on the plus side to 1.5x stock plus 10kPa, and to roll the 5/6 slip from 20 at low rpm to 10 at 2000 with a gradient in between, and reduce the adaptive to +/-5 psi. With that the slip logs close to zero under most conditions, so I think I am in an overshoot condition, where I have plenty of pressure to lockup at what the computer characterizes (guesses) at about 42-46 psi.
 

Foggy

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In hindsight, that is probably the understatement of the year. I was thinking all the mechanical improvement, regulation, better pressure, tight tolerances, stronger/straighter friction surfaces would help the computer to compensate less.

Because the computer guesses (I mean characterizes, haha) the actual pressures it could be doing things to create more hysteresis (fluctuation) instead of smoothing.

With the stock settings, the original red flag was a strong noisy shudder going up a steady incline in 5th at about 50mph and maybe a slight acceleration. It was the kind of drivetrain noise that makes you think u-joint failure because of the slight but rapid velocity changes in the driveshaft, resonating quite noticeably. I didn't actually log this condition, but it did present in a lesser form after some initial tuning, and it was quite evident that the measured TCC slip was yoyo-ing up and down rapidly. If I give the benefit of the doubt to the converter builder, such that the friction is good (lets say it mated nicely and has a good grip above a stock JBMX, and the TCC engagement quickly reduces slip such that the computer counters by reversing the pressure quickly causing a nasty slip/catch cycle which is shudder.

My current tune is to increase the TCC pressure (well below what others are using), bump the apply ramp on the plus side to 1.5x stock plus 10kPa, and to roll the 5/6 slip from 20 at low rpm to 10 at 2000 with a gradient in between, and reduce the adaptive to +/-5 psi. With that the slip logs close to zero under most conditions, so I think I am in an overshoot condition, where I have plenty of pressure to lockup at what the computer characterizes (guesses) at about 42-46 psi.
Put the slip to ZERO in 5th and 6th... I didn't see if you were still using the DOD/AFM
but that's a big reason why there is so much slip built in
Get rid of lock up in 1-3 gears altogether. Some say even 4th gear, but I like having
the lock up in 4th above 42 mph.
I also set my upshift part throttle shifts to something not so dumb..
No more hunting for gears and then bogging only to downshift
It just takes some patience and trials to get it where YOU want it. I have seen
no decline in MPG either. I really really enjoy my 6L80E now .. stock it sucked !!
 

iboughtatahoe23

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Pretty sure my TC is going… starting to get a light shudder when letting off the gas. And I’ve had issues with the trans ever since I got it 3 months ago. Wish I knew how to do that stuff man! I’d get at it no issue.
 

swathdiver

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Pretty sure my TC is going… starting to get a light shudder when letting off the gas. And I’ve had issues with the trans ever since I got it 3 months ago. Wish I knew how to do that stuff man! I’d get at it no issue.
One member here did a tutorial with lots of photos. The instruction sheets make things easier too.
 

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