'15 Silverado - M and Tow/Haul Modes NOT locking out AFM

Potts · September 24, 2015

Hey Folks - Need some help here... From everything I can gather reading posts, my understanding is that using either the "M" driving mode or by turning on Tow/Haul, the AFM would be locked out and the truck would not shift into V4 mode via the AFM system.

I have tried both, and when using either Tow/Haul or "M" mode (I set it to 6 - I have the 6 speed), I can still see the AFM activating and the engine switching into V4 mode via the indicator in the DIC.

Does this not work on the 2015's or am I missing something?

Thanks.

newdude · September 24, 2015

Tow/Haul, AFM will still work. You have to put in M but not M6, you need to put it in M5 to cancel out AFM.

Oh...and you don't have to "shift" the gears with the +- rocker, just put it in M, toggle to M5 and drive away. By setting it to M5, you are locking out 6th gear and disabling AFM. It will still shift itself, up or down, through gears 1 to 5.

Potts · September 24, 2015

Ah, I must have been confused. I swore I read tow/haul would also do it. Got it about M5, I will try that next time I go for a ride.

Can you shift into M on the fly, as in while moving?

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robvas · September 24, 2015

Can you shift into M on the fly, as in while moving?

Yes. Don't be alarmed if the truck downshifts though.

Potts · September 24, 2015

Thank you both.

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newdude · September 24, 2015

Yes. Don't be alarmed if the truck downshifts though.

Ah, I must have been confused. I swore I read tow/haul would also do it. Got it about M5, I will try that next time I go for a ride.

Can you shift into M on the fly, as in while moving?

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Quick story about that actually. My 2012 and others I have driven, if you switched to M from D, it would show and stay in whatever gear you are currently in. My 15HD, if you shift on the fly to M from D, it drops to 4th from 6th. Caught me off guard the first time I did it lol.

tnchevy · September 24, 2015

My 2014 1/2 ton does the same, goes to 4th when you put it in manual mode. I normally put mine in M5 when riding around the steeper hills around here.

Potts · September 25, 2015

Good to know. Depending on what I'm doing at the moment dropping two gears ain't always the best thing to have happen.

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tnchevy · September 25, 2015

I agree and the first times I did it was going at a pretty good clip at the base of one of the mountains I cross around here and dropped it to manual. I've since learned to wait till I was going below 45mph to go into manual. That is one thing I like alot about my F150 work truck is that you don't have to switch the shifter to manual, you can change the highest gear anytime you want. It still has a worse transmission than my chevy though.

Silverado-Hareek · September 25, 2015

I've basically gotten into the habit of putting the truck in M mode always instead of Drive. For instance going to work in the morning........I back out of the driveway, shift to M, click the button up to M5, and then start driving. When I hit sustained speeds of higher than 40 mph, I click it up to M6 to relieve the engine. And that's become a habit for me now. When driving around town, the truck behaves much better in M5 and I like the fact that all 8 cylinders are working, hopefully warding off any future problems caused by the AFM system like on the last generation trucks. I plan to keep this process up until the warranty runs out, at which point I will permanently disable AFM with a tune.

Potts · September 25, 2015

I think I'm gonna start doing that as well, although I do like the proposed fuel savings. Especially if I'm gonna start putting premium in it, which I'm considering after hearing all hear reports about improved power.

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tnchevy · September 27, 2015

I ran two tanks of 89 and one tank of 93 in my last 3 tanks and I saw/felt no extra power and my mpg were the same as 87 octane has been this summer. I think a lot of it is perception that the higher octane is giving you more power/mpg's.

mjj · September 30, 2015

I've tried the M5 thing, could never get into the habit of doing it on a regular basis. But I've been tuned for over 10k miles now. Probably half that time with AFM on and half with it off. I keep track of my mpg at every fill up and I can say for myself I have seen no more than a 0.5 mpg decrease with AFM off and in driving in D, mostly country 55mph roads and 70 mph highway driving.

redwngr · October 1, 2015

Owners manual has charts showing what gear the trans will be in after shifting from D to M.

-Depends on 6 speed or 8

-Depends on tow/haul engaged or not.

-And (of course) depends on what gear it was in in D, before the shift was made.

Grade Braking is not available when Range Selection (manual) Mode is active.

Cruise can still be used.

Tow/Haul Mode Grade Braking is only enabled while the Tow/Haul Mode is selected and the vehicle is not in the Range Selection Mode.

robvas · October 1, 2015

I've tried the M5 thing, could never get into the habit of doing it on a regular basis. But I've been tuned for over 10k miles now. Probably half that time with AFM on and half with it off. I keep track of my mpg at every fill up and I can say for myself I have seen no more than a 0.5 mpg decrease with AFM off and in driving in D, mostly country 55mph roads and 70 mph highway driving.

I want to turn my AFM back on and see what my gas mileage looks like for a month, but it's getting cold our and soon we'll have winter gas so that will throw my #'s off