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How is the DFM working for you?

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Thomcat Senior Enthusiast

Thomcat

Posted
Posted
On 12/23/2018 at 7:11 AM, steve841 said:

 

Me too ...  but my last truck was the 6 speed .. ran about 2200 RPMs at 70mph.

 

The 19 runs at around 1800 RPMs at 70mph.

 

Everything about that metric makes you think the 19 should kill the old truck in mileage.  Its simply not the case.

 

The only other major difference is the 19 has 22" wheels vs the old one with 20"

If yours came with the dealer installed OEM 22"s listed on the Maroney sticker the difference is the tire/rear end combo. My RST comes standard with a 3:42 standard rear but a check of the RPO codes lists a GU5 3:23 rear.....seems when you choose the larger/higher OEM 22" option it substitutes the 3:23 rear.....likely why the 5.3l DFM 8 speed seems a lot quicker than my former 5.3l AFM 6 speed.

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MacLaren
MacLaren

Honest to goodness, I cannot tell when it changes or whatnot. Absolutely seamless to me.  I love this truck. Great mpg, and has tons of power when ya need it. 

wizard4878
wizard4878

seemless operation and averaging over 20 mpg,  whats not to like?

Thomcat
Thomcat

It's not a matter of what could go wrong with the DFM or even a matter of better gas mileage.....it is a matter of designing a less complicated less trouble prone engine.   AFM systems were

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MacLaren Enthusiast

MacLaren

Posted
Posted

Honest to goodness, I cannot tell when it changes or whatnot. Absolutely seamless to me.  I love this truck. Great mpg, and has tons of power when ya need it. 

  • Like 3
AlaskaErik Enthusiast

AlaskaErik

Posted
Posted

No idea.  I have never noticed it on my 2019 6.2 vs my 2016 5.3 with AFM, which I do notice deactivating/activating at times.  Fuel mileage does seem better with the 6.2.  

  • Like 1
2016 Sierra Owner Senior Enthusiast

2016 Sierra Owner

Posted
Posted
On 12/13/2019 at 8:22 AM, 2cyclemech said:

LT All Star edition 5.3 eco L84 8speed trans 14K purchased in March of 19 

I sure hope they get it sorted out for you. I have not been able to tell when the DFM kicks in on my truck yet.

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madconcept Enthusiast

madconcept

Posted
Posted

Can’t notice it on my 2019 Sierra 5.3/8 speed.

My last 07 Silverado with the brand new of the day AFM was definitely noticeable, plus I drove with the instant fuel economy display on that showed when it went from 4 to 8.

 

Would actually be nice to have a display showing how many cyl are running at any given time.  Just because I’m curious to see when these trucks are actually only running on 1 cyl!

Thomcat Senior Enthusiast

Thomcat

Posted
Posted
11 hours ago, madconcept said:

Can’t notice it on my 2019 Sierra 5.3/8 speed.

My last 07 Silverado with the brand new of the day AFM AFM and DFM

 

Would actually be nice to have a display showing how many cyl are running at any given time.  Just because I’m curious to see when these trucks are actually only running on 1 cyl!

AFM and DFM on V8s operate deactivating opposing cylinders. A V8/V6 engine operating on 1 cyl is inherently unbalanced and you would not need a gauge to let you know when that happens when you accelerate or maintaining speed.......it may happen and they may promote it as a gimmick running on one cyl when coasting, but you could shut them all down and coast on 0 cyl also without noticing. Solution over AFM is getting rid of the LOMA manifold controlling half of the oil solenoids in the LOMA manifold with no oil control over the other half; and DFM having direct control direct computer control over all oil shutdown solenoids mounted directly in the block. Faster CPUs and more complex algorithms in place of an intermediate manifold make DFM feasible and the process seamless vs. the more complex ,outdated (likely discontinued) AFM system.

 

AFM worked properly in my Avalanches and '16 Silverado; however, on occasion, under the right conditions you could notice a slight difference during the transition verified by the V8/V4 monitor. But with DFM I've tried under the same conditions and can't feel a thing and without a gauge I have no idea whether DFM exists or is a myth......one thing is certain the same 5.3l DFM 8 speed feels like has a lot more power and faster acceleration than the former 5.3l AFM 6 speeds......or might be the 22"s with 3:23 rear opposed to the former 17"s and 18"s on 3:42 rears.

KARNUT Senior Enthusiast

KARNUT

Posted
Posted
AFM and DFM on V8s operate deactivating opposing cylinders. A V8/V6 engine operating on 1 cyl is inherently unbalanced and you would not need a gauge to let you know when that happens when you accelerate or maintaining speed.......it may happen and they may promote it as a gimmick running on one cyl when coasting, but you could shut them all down and coast on 0 cyl also without noticing. Solution over AFM is getting rid of the LOMA manifold controlling half of the oil solenoids in the LOMA manifold with no oil control over the other half; and DFM having direct control direct computer control over all oil shutdown solenoids mounted directly in the block. Faster CPUs and more complex algorithms in place of an intermediate manifold make DFM feasible and the process seamless vs. the more complex ,outdated (likely discontinued) AFM system.
 
AFM worked properly in my Avalanches and '16 Silverado; however, on occasion, under the right conditions you could notice a slight difference during the transition verified by the V8/V4 monitor. But with DFM I've tried under the same conditions and can't feel a thing and without a gauge I have no idea whether DFM exists or is a myth......one thing is certain the same 5.3l DFM 8 speed feels like has a lot more power and faster acceleration than the former 5.3l AFM 6 speeds......or might be the 22"s with 3:23 rear opposed to the former 17"s and 18"s on 3:42 rears.

It’d been interesting to here louder exhaust on the lasted GM Frankenstein, maybe not.


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hotrodz37 Senior Enthusiast

hotrodz37

Posted
Posted

Are any of you getting a rumble on deceleration? Mainly from 28-18 mph while the truck is shifting from 3rd to second gear? I took mine into the dealer as it feels like the torque converter clutch is locking up too long, but they don't think it's a transmission issue, but agreed its there. I tried it in L7 which is supposed to get rid of DFM and it still does it - but in neutral it completely goes away. Thinking it might be DFM lugging the engine down but not sure.

 

Just checking to see if any of you are having this issue. Thanks! 

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted (edited)

When I stand on one foot and gargle hot sauce with my hands over my ears I fart blue flames. When I had AFM it was smoke out my ears but now that I have DFM its flames. Is there something wrong with my second cousins dog?

 

:crackup: 

 

It's about the same as reading; My 2020 GM with it's 20% larger frontal area get's the same mileage as our 2015 did towing our 10,000 pound trailer at 70 mph. It's obvious the 10 speed and DFM just doesn't work.

 

:banghead: 

 

OR, I had a massive lifter failure and they replaced the lifters, cam and VLOM because the screens were plugged with varnish. The VLOM system is a piece of junk. DFM will be much better. Electrical parts never fail unless they are driving solenoids controlling oil. Ones controlling something else are much more reliable. Plus you can run your oil forever. 

 

:wtf:

 

 

 

Edited by Grumpy Bear
jlong1984 Enthusiast

jlong1984

Posted
Posted
18 hours ago, hotrodz37 said:

Are any of you getting a rumble on deceleration? Mainly from 28-18 mph while the truck is shifting from 3rd to second gear? I took mine into the dealer as it feels like the torque converter clutch is locking up too long, but they don't think it's a transmission issue, but agreed its there. I tried it in L7 which is supposed to get rid of DFM and it still does it - but in neutral it completely goes away. Thinking it might be DFM lugging the engine down but not sure.

 

Just checking to see if any of you are having this issue. Thanks! 

Nope, outside of the hard 1-2 shift in the morning, both my engine and transmission are smooth as butter. DFM is seamless, unlike the AFM in my '14 and '16. 

Weimrunner Enthusiast

Weimrunner

Posted
Posted

Have to say I couldn’t feel or notice a difference til I had my first oil change then it changed. At low speeds in town, 20 to 30 mph, I notice the shutter in my seat and steering wheel. I know the feeling cause my wife’s ‘19 Yukon Denali has the same terrible feeling while cruising at highway speeds. Any insight on a problem that developed during the oil change and fix or do I have to deal with it?

2019 GMC Crew 4x4 AT4 with 5.3 and 8speed transmission. 9000 miles.

Thomcat Senior Enthusiast

Thomcat

Posted
Posted
On 1/26/2020 at 10:11 AM, Weimrunner said:

Have to say I couldn’t feel or notice a difference til I had my first oil change then it changed. At low speeds in town, 20 to 30 mph, I notice the shutter in my seat and steering wheel. I know the feeling cause my wife’s ‘19 Yukon Denali has the same terrible feeling while cruising at highway speeds. Any insight on a problem that developed during the oil change and fix or do I have to deal with it?

2019 GMC Crew 4x4 AT4 with 5.3 and 8speed transmission. 9000 miles.

Sure you're getting the correct oil 0W-20 and PF63E filter....0W-20 is necessary for the operation of the solenoid valves and collapsible DFM lifters. Unless you see or confirm with empty bottles always the possibility of pulling from the wrong bulk drum or worse e.g. 10W30 fits all.

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