2012 Silverado lunges forward while braking to a stop

[CKN]

Originally Posted By: SteveSRT8
Originally Posted By: CKN
No. AFM engages at lower speeds as well.Even when your slowing down to stop. You Post is incorrect. However-it will only engage at all speeds when selector is in D or manual 6th position. If manual selector is in 5th or lower it will not engage.



Thanks for that. My experience is only with 3500 6.0/6L90E service vans and they are programmed completely different than even 3500 6.0 Silverados. I would still suggest OP's issues are unrelated to AFM...


If the AFM "engages" upon deceleration-you will get the situation the OP described. Sure-we can agree to disagree.

 

[SilverFusion2010]

Check with a dealership, there may be an engine/transmission programming update available. My fusion does the reverse effect as it downshifts. 2-1 gives considerable braking assistance if you're slowing down approaching a stop. I think this is due to the aggressive fuel trim ford has programmed into this engine. If you're not on the gas it basically cuts all the fuel from what I understand.

What you are describing is alarming. When stopping a sudden thrust forward is not good.

Try throwing it in neutral as you stop. Should eliminate the lurch

 

[Oil_Flunky]

It could be transmission stick slip. If you serviced the transmission by only changing the filter and cleaning the pan, chances are you only replaced half the fluid. Try fluid replacement with Dexron 6 and or Lubegard platinum.

 

[AVB]

Originally Posted By: Oil_Flunky
It could be transmission stick slip. If you serviced the transmission by only changing the filter and cleaning the pan, chances are you only replaced half the fluid. Try fluid replacement with Dexron 6 and or Lubegard platinum.

What is stick slip?

 

[Oil_Flunky]

Stick slip:"is the spontaneous jerking motion that can occur while two objects are sliding over each other." When the transmission is downshifting the degraded friction modifiers in old or contaminated (clutch material etc.) fluid can cause stick slip.

((EDIT: I had this condition with a 2010 Silverado AFM 4x4 crew cab 5.3 6 speed auto black in color , new fluid fixed it, lubegard added because I had it and deemed it not to hurt but most likely help. YMMV))

 

[SteveSRT8]

Originally Posted By: CKN
No. AFM engages at lower speeds as well.Even when your slowing down to stop. You Post is incorrect. However-it will only engage at all speeds when selector is in D or manual 6th position. If manual selector is in 5th or lower it will not engage.


No, my post is correct for many heavy duty applications. They absolutely do NOT all have identical programming or behavior.

Note that our 3500 service vans will not even go into 6th gear until around 52 mph no matter what you do. Roar at full throttle to 50 and let off and the trans will stay in 5th. All the shift points are elevated without regard for fuel economy.

While in your experience I am sure things are much different, I do not really disagree with you. You simply cannot label ALL AFM equipped vehicles as the same...

 

[AVB]

Originally Posted By: Oil_Flunky
Stick slip:"is the spontaneous jerking motion that can occur while two objects are sliding over each other." When the transmission is downshifting the degraded friction modifiers in old or contaminated (clutch material etc.) fluid can cause stick slip.

((EDIT: I had this condition with a 2010 Silverado AFM 4x4 crew cab 5.3 6 speed auto black in color , new fluid fixed it, lubegard added because I had it and deemed it not to hurt but most likely help. YMMV))


I have never heard that term before. We would call that a shudder.

 

[Olas]

Manuals don't have these problems.