6L90E shuddering when converter locked and under load

[Jim_PA]

In 3rd or 4th gear under a load like when going up a decent hill, I can feel some shuddering or slipping of the torque converter. Is there something that can be adjusted to try to tune out the shudder or slipping or whatever might be going on?

I see the ramp in D2216 and some TCC slip tables that I feel might be able to help some of this, but I'm not sure where I should start..

Thanks

[Jim_PA]

Any ideas? It's mainly in 5th when going up a grade. Feels like an engine miss, but it's only when the converter is locked

[Jim_PA]

I feel like the converter is trying to hold on too long, like it shouldn't even be locked when it does this. Maybe I can figure out how to make it unlock sooner. TP% unlock maybe?

[joecar]

Is the ECM tune modified...? If so have the torque model tables been adjusted...?

[Jim_PA]

Is the ECM tune modified...? If so have the torque model tables been adjusted...?

Yes, the ECM is modified (PE delay, timing, other small things), and the torque model tables were increased by 15% I also decreased desired upshift times 10%

However, this problem existed before I ever touched anything. Thinking about throwing in a bottle of instant-shudder fix.

There is a TSB that I wish I could see, but apparently it's no longer available or expired.

POWER TRAIN:AUTOMATIC TRANSMISSION
Bulletin Number:
09-07-30-001 Bulletin Date:
Mar 2011
Summary:
GM: WHEN DRIVING AT HIGHWAY SPEEDS THERE MAY A SHUDDER OR BUCKING FEEL AT HIGHWAY SPEEDS. ( NHTSA ITEM NUMBER - 10038263 )

Found the tsb here, with a guy that 100% accurately describes the problem I have http://community.cartalk.com/discussion/2300239/shudder-going-uphill

I'd like to try increasing the TCC lock-up pressure (not the ramp-in) but it seems I can't figure out how to do that.

[Taz]

That particular TSB only applies to the 2 Mode Hybrid automatic transmission (M99) not the 6L80 (MYC) or 6L90 (MYD).

[Jim_PA]

That particular TSB only applies to the 2 Mode Hybrid automatic transmission (M99) not the 6L80 (MYC) or 6L90 (MYD).

Darn. Thanks Taz!

[Jim_PA]

If it comes down to it, I will probably just try to unlock the converter at the specific speeds/TPS% conditions it's doing it under (it's very consistent!) but was hoping to find a fix in the tune rather than disabling a ... feature. I wonder if I can find a 2013/14 6L90e tune to see if the calibration is different or maybe improved in some way that avoids this issue.

[Taz]

... I'd like to try increasing the TCC lock-up pressure (not the ramp-in) but it seems I can't figure out how to do that ...

Those parameters are not available in EFILive.

Post your tunes, and perhaps I can help.

[Jim_PA]

Those parameters are not available in EFILive.

Post your tunes, and perhaps I can help.

Ahhh -- OK! I don't know if those parameters would help or not, but it would be nice to bump up the pressure to see!

Here are my stock and modified files. Thanks for offering to look! it's a 2010 Suburban 2500 LY6/6L90e (no AFM)


18025
18026
18027
18028

Oh, and P.S. I have tried the self-clean and re-learn procedures, they didn't seem to do much.

[Taz]

I reworked your stock TCM tune ... set the TCC slip RPM to zero for all gears (like a Corvette) given that you don't have AFM. I also increased the TCC pressure ramp in rate, and the TCC pressure (this is the only parameter changed that is not available in EFILive).

Hopefully this helps ...

[Jim_PA]

I reworked your stock TCM tune ... set the TCC slip RPM to zero for all gears (like a Corvette) given that you don't have AFM. I also increased the TCC pressure ramp in rate, and the TCC pressure (this is the only parameter changed that is not available in EFILive).

Hopefully this helps ...

Whatever it was, I think you got it! I have a little bit of low-speed off-throttle sensation that I didn't have before, but it beats the bucking that I was experiencing that appears to be gone!


Thank you!

[Taz]

You are very welcome ...

Work with D2216 (TCC Lock Pressure Ramp) to see if you can smooth out the low throttle sensation ... if you compare the tune I posted with your stock tune, you will see where I increased the slope of the pressure ramp ... perhaps a little too much in the lower torque output areas.

[joecar]

Good job :cheers:

[CalebTheCarNinja]

Yeah, I was having the same issues with my 6L90. tried looking it up everywhere to no avail... I even took it to my local shop (small town) and the guys there didn't know what to do with it...

So I went online to find a remanufactured 6L90 transmission and found this place https://reman-transmission.com/transmission-codes/?code=6L90 They sent it out and was at my door in a couple/few weeks time.. Then all I had to do was take it to the mechanic, have it installed and I was sittin pretty in my 3500 again :)

[joecar]

What did the reman shop find as the problem/cause...?

[Dave_villa]

I had the same problem with my 6L90 transmission and couldn't find a solution anywhere. I even took it to my local shop, but they didn’t know how to fix it.

Then I found a remanufactured 6L90 transmission online at https://bestqualityautoparts.com/transmissions/ . They shipped it to me in a couple of weeks. Once it arrived, I took it to my mechanic, got it installed, and now my 3500 is running great again!