2015 active fuel management system.

[NMS_1013]

I've had this truck for about 6 months and noticed a hard downshift or even clunk at times when rolling around a corner or letting off the gas. I was told that this has to do with the fuel management system, being when it changes from 4-8 cylinder mode. You can override that by starting from park directly to M5 and that basically turns off this feature. I was told by GM that the clunk shouldn't be an issue was designed that way. That also came from a kid who wasn't even 30 years old. I just want to see if anyone has experienced the same thing and or if there is something that a dealer can do to fix this. Like I said, doesn't happen all the time, but just doesn't sound right.

 

 

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[15_silverado]

It has just about nothing to do with the AFM. When you drive in M5; with the AFM off does it still clunk?

 

Pretty much all or most of these trucks have this problem. It's transmission related or transmission tuning related.

 

And per GM is " operating as normal"

Not happy about that answer; but there's nothing they can or will do.

[djxn40]

I've had this truck for about 6 months and noticed a hard downshift or even clunk at times when rolling around a corner or letting off the gas. I was told that this has to do with the fuel management system, being when it changes from 4-8 cylinder mode. You can override that by starting from park directly to M5 and that basically turns off this feature. I was told by GM that the clunk shouldn't be an issue was designed that way. That also came from a kid who wasn't even 30 years old. I just want to see if anyone has experienced the same thing and or if there is something that a dealer can do to fix this. Like I said, doesn't happen all the time, but just doesn't sound right.

 

 

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Hmm. It's funny you post this now. I've had my 2016 z71 for almost 6 months. I also had the clunking... sometimes bad! After 3 months I bought a programmer. I turned off fuel management for other reasons. I haven't thought much about the clunking till you posted this. But I must say I haven't had a single clunk since I used the programmer.

Maybe they are right about the fuel management after all... or maybe it's the tyranny side as I tuned that as well. I have no regrets as far as the programmer... Wouldn't own this truck without it

 

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[Knotsure]

I think it is the transmission programming. I was driving my bosses 2012 sierra with 5.3 and 6 speed auto trans, and I realized how much more I like how his starts off and drives in general. It feels like it has more power from the get go and shift s smoother across the board in my opinion. After the Initial takeoff I can feel the more power and all that in my truck, there is just a huge difference in his transmission shifting and mine.

 

 

2014 Chevy silverado Z71 DCSB w/Bilstein 5100 level

[15_silverado]

Hmm. It's funny you post this now. I've had my 2016 z71 for almost 6 months. I also had the clunking... sometimes bad! After 3 months I bought a programmer. I turned off fuel management for other reasons. I haven't thought much about the clunking till you posted this. But I must say I haven't had a single clunk since I used the programmer.

Maybe they are right about the fuel management after all... or maybe it's the tyranny side as I tuned that as well. I have no regrets as far as the programmer... Wouldn't own this truck without it

 

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I using a range AFM disabler, but still get some light clunking, popping, clicking sounds. This happens when coming to a stop; and more so a fast stop. Also when coasting down hill; totally off the throttle; when the trans lets go of the gear it's currently in and grabs the next gear up. Again, the range AFM disabler has not changed these clunking problems/noises.

 

Nothing bad to say about the range though, it's doing its job perfectly; and I'm very happy to get rid of the V4 mode.

 

So my question for you is what tuner are you using and if you know how you have any of your settings set?

 

Also are you saying that you had the clunking as discribed and after the tuner it has completly gone away?

 

Thanks.

[NMS_1013]

Hmm. It's funny you post this now. I've had my 2016 z71 for almost 6 months. I also had the clunking... sometimes bad! After 3 months I bought a programmer. I turned off fuel management for other reasons. I haven't thought much about the clunking till you posted this. But I must say I haven't had a single clunk since I used the programmer.

Maybe they are right about the fuel management after all... or maybe it's the tyranny side as I tuned that as well. I have no regrets as far as the programmer... Wouldn't own this truck without it

 

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. What programmer are you running and what's tune settings? If that seemed to fix it for now I'm all for a try!

 

 

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[newdude]

Its backlash. Total backlash between the transmission gear sets, front and rear differentials. Those clunks with the 6 speeds have been around since 2007 in the Denali and Escalade, and in pickups since 2007 (HD) and 2010 (1500). My 2015 HD with the 6L90 does it. It is normal.

[Jeff5347]

I don't know if anyone has felt this but I can definitely feel my AFM kicking on or off. Meaning I usually have it in m4 or m5 if I'm around town or whatnot. When I get on the highway I shift up to m6. On the highways in Mass there are hills and descents and whether it goes into v8 or v4 its very noticeable. The other day coming home up a hill on the highway I had the DIC on that shows the AFM mode. Started going up hill, no change in throttle and as soon as it went from m4 to 8 I felt a kick like you would a shift. Is it normal to feel the AFM going in and out. Its not just a little bump, definitely can feel it

 

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[Slugworth]

What settings did you use for the tranny??

[newdude]

I don't know if anyone has felt this but I can definitely feel my AFM kicking on or off. Meaning I usually have it in m4 or m5 if I'm around town or whatnot. When I get on the highway I shift up to m6. On the highways in Mass there are hills and descents and whether it goes into v8 or v4 its very noticeable. The other day coming home up a hill on the highway I had the DIC on that shows the AFM mode. Started going up hill, no change in throttle and as soon as it went from m4 to 8 I felt a kick like you would a shift. Is it normal to feel the AFM going in and out. Its not just a little bump, definitely can feel it

 

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GM says its seamless, yet I have always felt it. Normal. Now, if you try driving a Camaro or Corvette or an 06-09 Impala SS, its seamless. The added mass of the trucks makes it noticeable, but in the cars you would only know from the sound change. Real smooth in those.

[Donstar]

My previous '09 had and my current truck has AFM. I have tried to detect when these trucks switch in or out of V4 without the aid of the display. I have been unsuccessful as the switch is seamless. If it became noticeable then I would get my truck serviced. Driving around in M5 to avoid the discomfort of switching is ignoring a needed repair, imo.

[amxguy1970]

What does the guy being under 30 have to do with it? Probably better trained and informed than most anyone here, a forum you decided to join to get an answer...

 

Tyler

[MrNasty]

Felt AFM in my 2015 6.2 and when i had a 2016 5.3 for a loaner for 4 weeks while my transmission was being fixed i felt it. I also felt it in my wifes 2015 5.3. So maybe some are seemless but the three i have driven with AFM were not.

 

 

 

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[Grjfer]

I have embraced AFM for 9+ years. I purchased my 08 Silverado 5.3 in December of 07, drove it for 9 years, and never once knew it was activated accept for the V4 indicator on the dash. It never kicked in till the truck was up to operating temp, and it only took a slight amount of pressure to deactivate.

 

My 15 Sierra 5.3 is far from seamless. It will activate at coolant Temps below 170. Takes more pedal pressure to deactivate, and it shudders and vibrates when active. So take that for what it's worth

[vranasaurus]

I haven't been able to detect anything with my 2010 or 2015 5.3's when going into and out of V4. The only way I know is if I look at the display.