TRNW-2: Chevy Active Fuel Management Killing 6L80's?

Wed Jun 18 16:25:41 PDT 2025

I hope I never see a 4L60E again.

On Wed, Jun 18, 2025 at 3:32 PM Jim Bockus via trnw2 <trnw2 at trnw.net> wrote:

> So true, I still see a lot of 4L60E's but they are time consuming compared
> to the 6L80's and usually take more parts and less profit.
>
> On Jun 18, 2025 1:28 PM, Justin Merritt via trnw2 <trnw2 at trnw.net> wrote:
>
>
> Once you get good and comfortable with the 6Ls, you will never want to see
> a 4l60 again!!!
>
> Justin
>
> On Wed, Jun 18, 2025 at 12:47 PM Tony's Autoworks via trnw2 <
> trnw2 at trnw.net> wrote:
>
> Thank you all for your comments. I talked to another transmission shop
> this morning and this situation has just the new kid in the block when
> it comes to engine issues that can't be diagnosed before the
> transmission rebuild. In the end, we can only fix what we see to be
> broken. From there, just make the best of the situation.  I have the
> HP Tuner and have used it mainly to copy and paste techem software and
> for live data diagnosis. I can use it to disable the AFM and am
> looking at what to change for the TCC lock up strategy. As we are
> starting to see the 4L60's fade away and the 6L80's clocking over
> 100K, I guess we do what we have always done. Roll with the punches.
>
> Tony
>
> On Wed, Jun 18, 2025 at 10:25 AM Steve Everett via trnw2 <trnw2 at trnw.net>
> wrote:
> >
> >
> >   As Dan said , if the customer brings the vehicle in when they first
> notice the tcc shudder,  those clutches will be like new, and the pump
> won't be damaged enough to worry about,  usually not damaged at all ,
>  there might be a teaspoon of material in the pan,  the PR valve will be
> worn, and the tcc reg valve bore will be worn,  address those and delay
> lockup until 5th gear , I usually set them around 45mph,   the exception
> being if its a truck that tows around town I'll have it lockup in 4th gear
> and at 40mph,   so that it will lockup at around town speeds and not
> overheat while towing
> >
> >     Steve
> >
> > On Wed, Jun 18, 2025 at 12:46 PM Dan Hogan via trnw2 <trnw2 at trnw.net>
> wrote:
> >>
> >> 456 clutch failures are not related to AFM in my opinion.  I agree with
> Steve as most 456 failures are the result of excessive metal debris related
> to converter issues resulting in restricted pressure and sticking valves /
> filters.  Customers who bring their vehicles on the front end of converter
> failures tend to have intact 456 clutches.  The ones who keep on getting it
> until the vehicle won't move or slipping badly on highway drives tend to
> arrive with a roasted 456 clutch.  Usually can hear the pump whining at
> this point as well.
> >>
> >> How are you dealing with the converter clutch failure debris in the
> cooler system?  We still have local shops who don't flush or do anything
> besides a can of flush and install a unit or rebuild and wonder why they
> have repeat failures.  I don't do carry-out work anymore as I don't want to
> fight these folks. The amount of debris from these failures is
> significant.  Even hot flushes sometimes don't get all the debris out of
> the system.
> >>
> >> I'd look over your methods to manage contamination as it's a big deal
> and I suspect the main cause of rework.
> >>
> >> Now diagnosing AFM malfunctions vs TCC shudder can be difficult and
> most dealers don't have the personnel to do fine level diag work from what
> I see and hear now.  It's just swap until fixed and customer gets to pay.
> I don't recommend any young folks get involved with dealers at all anymore.
> >>
> >>
> >>
> >> ---
> >>
> >>
> >> Dan Hogan
> >>
> >> Buster's Transmission Service
> >>
> >> https://busterstransmission.com
> >>
> >> 704.847.5321
> >>
> >> ________________________________
> >> From: trnw2-bounces at trnw.net <trnw2-bounces at trnw.net> on behalf of
> Tony's Autoworks via trnw2 <trnw2 at trnw.net>
> >> Sent: Tuesday, June 17, 2025 8:52 PM
> >> To: Technical Discussion Forum <trnw2 at trnw.net>
> >> Subject: TRNW-2: Chevy Active Fuel Management Killing 6L80's?
> >>
> >> Hello group,
> >>
> >> Wanted to get an opinion of what I have seen over the last 3 months. I
> >> have rebuilt six 6L80/6L90 and have had a few other vehicles come in
> >> the door with similar problems that I will explain in a moment. Of the
> >> 6 I rebuilt, all had 4-5-6 clutch stacks completely burnt and 3 of the
> >> 6 had pumps that were not reusable. Of the 6, 2 of them were towed in
> >> with no movement. Just finished the 2nd of the two yesterday and
> >> completed a test drive for the new techem to adapt. But noticed both
> >> towed in units having some issues but could not determine the cause
> >> until now. After a certain amount of time test driving I'm noticing
> >> rpm fluctuations and an intermittent shudder noise on the most recent
> >> unit. Checking scan tool data the TCC is applying and no TCC RPM slip
> >> is occurring when the shudder happens. I noticed the same issues on
> >> the last unit but NO shudder until today the customer told me he
> >> experienced it and I just test drove to confirm.
> >>
> >> I also have a customer with a 2015 Suburban that had a transmission
> >> installed a few weeks prior from a different city and started
> >> experiencing the shudder issue. He thought maybe he had a defective
> >> torque converter. I noticed the shudder in the Suburban sounded
> >> different from the shudder in the silverados so I thought maybe the
> >> converter was defective. The suburban customer took the vehicle to the
> >> dealership and they diagnosed the Active Fuel Management causing the
> >> shudder when the system is activated and recommended a new engine or
> >> complete replacement of all AFM components.
> >>
> >> I took my recent rebuild on another test drive and with the traction
> >> control off (a friend from the chevy dealer advised this test) and now
> >> there are no RPM fluctuations and no shudder. Same with the other unit
> >> with similar issues.
> >>
> >> So now I have 2 units that have been rebuilt that looks like the
> >> Cylinder displacement may have been the cause of failure? My friend at
> >> the Chevy dealer says they are seeing a lot of these units come in and
> >> if they catch them in time they can save the transmissions. And most
> >> are replacing the engine rather than components.
> >>
> >> My question is this: Unless there are engine codes to know that the
> >> Cylinder displacement is an issue, how do we sell the build?
> >> Especially if the vehicle can not be test driven. I have 2 customers
> >> that have spent money on rebuilt units but now are looking at twice as
> >> much to fix the engine issues.
> >>
> >> I'm sure this topic has come up before and I guess I missed the memo.
> >> Just curious of your opinion and what have you done to diagnose this
> >> issue before selling a build.
> >>
> >> Thanks for reading,
> >> Tony
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> >> TRNW Inc., 2825 Walnut Terrace, Modesto, CA 95355
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> >
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> > TRNW Inc., 2825 Walnut Terrace, Modesto, CA 95355
>
> This message was sent from the TRNW Technical Discussion Forum (trnw2).
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> TRNW Inc., 2825 Walnut Terrace, Modesto, CA 95355
>
>
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> TRNW Inc., 2825 Walnut Terrace, Modesto, CA 95355

-- 
Pat Schulte
AAMCO Transmissions
Temecula, Ca.
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