Gear shifter buttons

hotrodz37 · January 7, 2020

Did anyone ever figure out for certain if L7 or L6 tunes out DFM? I am chasing down a problem I think might be related to DFM but am not certain if it gets rid of it since there's no indication on the dash anymore.

Thanks in advance!

Edited January 7, 2020 by hotrodz37

MacLaren · January 7, 2020

One thing for sure, when foing down a steep mountain that downhill assist button does great!

I prolly would worry with a manual shifting unless I was carrying a heavy load.

OnTheReel · January 8, 2020

4 hours ago, hotrodz37 said:

Did anyone ever figure out for certain if L7 or L6 tunes out DFM? I am chasing down a problem I think might be related to DFM but am not certain if it gets rid of it since there's no indication on the dash anymore.

Thanks in advance!

Yes, for certain it does. L7 on an 8 speed, L9 on a 10 speed.

You can confirm this by driving at a speed in which top gear wouldn’t be attained anyway. Get the truck moving at a steady speed, steady throttle input, then click from L7 to L8 (or L9 to L10 on a 10 speed), back and forth.

The trans won’t downshift or upshift between the two gear selections, but you should hear and feel a slight difference. That is the DFM engaging and disengaging between the two gear selections. DFM won’t be active in L7, but will be in L8 (same, but with L9/L10 in ten speeds).

L8 and L10 are literally the same as drive because in manual mode you are only selecting the maximum gear it will shift into. So obviously if you do the test at a speed in which the truck would be in the top gear, it will downshift / upshift between 8 and 7, and the experiment won’t work. Have to do it when the trans won’t shift, and then the only difference from 7-8 or 9-10 will be DFM or no DFM, much easier to pattern.

hotrodz37 · January 8, 2020

Yes, for certain it does. L7 on an 8 speed, L9 on a 10 speed.

You can confirm this by driving at a speed in which top gear wouldn’t be attained anyway. Get the truck moving at a steady speed, steady throttle input, then click from L7 to L8 (or L9 to L10 on a 10 speed), back and forth.

The trans won’t downshift or upshift between the two gear selections, but you should hear and feel a slight difference. That is the DFM engaging and disengaging between the two gear selections. DFM won’t be active in L7, but will be in L8 (same, but with L9/L10 in ten speeds).

L8 and L10 are literally the same as drive because in manual mode you are only selecting the maximum gear it will shift into. So obviously if you do the test at a speed in which the truck would be in the top gear, it will downshift / upshift between 8 and 7, and the experiment won’t work. Have to do it when the trans won’t shift, and then the only difference from 7-8 or 9-10 will be DFM or no DFM, much easier to pattern.

Thanks for the info! I am trying to figure out an issue on deceleration between 2nd and first gear so I guess even if I have it in L7 or L6 when I’m coming to a stop DFM might still engage in the lower gears it seems huh?

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OnTheReel · January 8, 2020

Nope, it’ll be totally off.

I just meant for the purposes of comparison, you can cruise around at just about any speed (assuming it’s not too fast) and literally use the + & - to turn DFM on and off instantly without affecting anything else. I found that helpful to learn the DFM tendencies and the NVH it adds at different speeds.

BUT if you’re just trying to check a deceleration vibration, obviously you don’t have to bother with that necessarily. Just leave it in L7 and it won’t be dropping cylinders. You can drive a route in L7, click it up to L8, drive the same route and compare.

Streetz · March 7, 2020

Hey folks, I have been experimenting with my 2019 and I want to add some observations to this thread, some which have already been confirmed but adding it anyway.

I installed a cutout so now I can hear everything that the engine is doing, which is wild how many variations of sounds it makes.

Driving in L7 does in fact disable DFM on all gears up to 7. Once you set it to L8 then DFM turns on right away, for example if you're cruising at 40 or 60 in L7, then change it to L8 or move the shifter to Drive, you will hear it change the tone to the helicopter sound that's been mentioned before on louder exhausts. This week iv driven in mostly L7 and let me tell you, it makes the truck much funner to drive.

I also have been messing with the sport mode in combination with L7 and I have noticed that when in sport mode the torque converter takes longer to lock up, I think it still locks at the same speeds but it takes longer before it engages while in normal mode the converter wants to lock almost all the time, even at very low speeds vs. the traditional 40mph lock up on older cars/trucks.

In regards to fuel consumption I do not have enough data yet but from what I can see, letting it go into 8th gear and turn on DFM does give you better milage (the live MPG indicator goes all the way full). So moving forward if I am doing some city driving with a lot of stop and go, i'll be putting it in L7. If I am going to cruise on the highway i'll leave it in drive or L8. If I want to have fun, L7 and sport mode.

redwngr · March 7, 2020

On 1/7/2020 at 4:03 PM, MacLaren said:

One thing for sure, when foing down a steep mountain that downhill assist button does great!

I prolly would worry with a manual shifting unless I was carrying a heavy load.

Next time, try it in auto and tow/haul and see what you think...

John Ladolcetta · March 12, 2020

On 2/24/2019 at 11:25 PM, Robwcormack said:

My gear shifter has plus and minus buttons for what seems like should allow you to manually shift gears. Problem is, they dont do anything at all when pressed. Anyone got any ideas of why?

Did you ever find out why the plus or minus does not work? I have a 2020 Sierra and mine does not work. I have an appointment with dealer.

Edited March 13, 2020 by John Ladolcetta

davester · March 12, 2020

Did you shift into "L" before trying the buttons?

OnTheReel · March 12, 2020

If he didn't, it's gonna be a real short and embarrassing appointment at the dealer...

redwngr · March 12, 2020

...deleted

Edited March 12, 2020 by redwngr

f8l vnm · March 12, 2020

anyone else wish GM would let you know what gear your in like RAM and Ford do in the gauge cluster ?

Like 1 through 10 i mean. I mean its not a real world problem as some of you say but i just think it would be a small detail that customers would appreciate.

bamorris2 · March 13, 2020

anyone else wish GM would let you know what gear your in like RAM and Ford do in the gauge cluster ?

Like 1 through 10 i mean. I mean its not a real world problem as some of you say but i just think it would be a small detail that customers would appreciate.

Yes, I miss this from my F150.