Interesting... progress with odd trans behavior? (2015 6-speed)

[DCazares]

This made a huge difference in my truck (14' 29k miles). It stopped the sluggishness it had and feels like a completely different truck as far as acceleration, down shifting and slowing down since it is not trying to engine brake on its own. Thanks for sharing.

[redwngr]

There is more than one grade braking mode.

 

Normal Mode Grade Braking

If equipped with a gasoline engine and an automatic transmission, Normal Mode Grade Braking is enabled when the vehicle is started, but is not enabled in Range Selection Mode. It assists in maintaining desired vehicle speeds when driving on downhill grades by using the engine and transmission to slow the vehicle. The first time

the system engages for each ignition key cycle, a DIC message will be displayed. See Transmission Messages 0 159.

To disable or enable Normal Mode Grade Braking within the current ignition key cycle, press and hold the Tow/Haul button for five seconds. When the button is released, the requested mode change is made. A DIC message displays. See Transmission Messages 0 159.

For other forms of grade braking, see Tow/Haul Mode 0 290 and Cruise Control 0 304.

Tow/Haul Mode Grade Braking

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.

See “Tow/Haul Mode” listed previously and Manual Mode 0 288.

Tow/Haul Mode Grade Braking assists in maintaining desired vehicle speeds when driving on downhill grades by using the engine and transmission to slow the vehicle. On vehicles with a gasoline engine, to disable or enable Tow/Haul Grade Braking within the current ignition key cycle, press and hold the Tow/Haul button for five seconds. When the button is released, the requested mode change is made. A DIC message is displayed. See Transmission Messages 0 159.

On vehicles with a diesel engine, Tow/Haul Mode Grade Braking can be enabled or disabled by pressing the Tow/Haul Mode button. Use the exhaust brake and Tow/Haul Mode for maximum grade braking.

See Towing Equipment 0 338.

For other forms of grade braking, see Automatic Transmission 0 284 and Cruise Control 0 304.

Cruise Grade Braking

Using Cruise Control on Hills

How well the cruise control works on hills depends on the vehicle speed, the load, and the steepness of the hills. When going up steep hills, pressing the accelerator pedal may be necessary to maintain vehicle speed.

While going downhill:

. Vehicles with a 6-speed automatic transmission and a gasoline engine have Cruise Grade Braking to help maintain driver selected speed.

Cruise Grade Braking is enabled when the vehicle is started and cruise control is active.

It is not enabled in Range Selection Mode.

It assists in maintaining driver selected speed when driving on downhill grades by using the engine and transmission to slow the vehicle.

To disable and enable Cruise Grade Braking for the current ignition key cycle, press and hold the Tow/Haul button for five seconds. A DIC message displays. See Transmission

Messages 0 159.

. Vehicles with a diesel engine have Cruise Grade Braking enabled when Tow/Haul Mode is on, the exhaust brake is on, or both are on.

All 3 "enable or disable" if tow/haul is pressed and held for 5 seconds.

"Normal mode grade braking" works when grade braking is enabled. (and is enabled when the vehicle is started)

"Tow/haul mode grade braking" requires grade braking AND tow/haul to be enabled

"Cruise Grade Braking" requires grade braking enable AND cruise control active

Bonus points if you can find a salesman that understands how this works. (but that's a discussion for another thread)

Manual doesn't say anything about the 8 speed, but on hilly terrain with the cruise activated I've had both the current 5.3/8spd and the previous 6.2/8spd perform a downshift to try and prevent the truck from running above the speed the cruise was set to. (and it takes a long, steep grade)

I definitely need to try running with it disabled.

[14silverado4.3]

Funny they all say downhill grades but it sounds like some programming eff up because it is doing it on any grade. Probably the slight forward rake of the truck is tricking the computer!

[BIGDOGx]

First call to gm is in, they also pointed me to this site https://www.gmideas.com/gmideas/ideas?action=NewIdea and wrote out my concern and suggest this option be defaulted to off.

 

I will continue to call them and i saved and will post up my suggestion on this website every week until i am 100% satisfied or i no longer own the truck!

[The Mad Veteran]

First call to gm is in, they also pointed me to this site https://www.gmideas.com/gmideas/ideas?action=NewIdea and wrote out my concern and suggest this option be defaulted to off.

 

I will continue to call them and i saved and will post up my suggestion on this website every week until i am 100% satisfied or i no longer own the truck!

 

Do you have a draft of what you typed out and sent to them? If so can you post it on here so all of us can copy and paste it on this website? Hopefully they do something about this since it should be an easy fix for them.

[Shu]

First call to gm is in, they also pointed me to this site https://www.gmideas.com/gmideas/ideas?action=NewIdea and wrote out my concern and suggest this option be defaulted to off.

 

I will continue to call them and i saved and will post up my suggestion on this website every week until i am 100% satisfied or i no longer own the truck!

Thanks for the link. I submitted a request for reprogram of transmission control module.

[Edelman13]

Funny they all say downhill grades but it sounds like some programming eff up because it is doing it on any grade. Probably the slight forward rake of the truck is tricking the computer!

That actually might make sense! I put bilsteins on and from day 1 I always felt the truck shifted better! It still would have, what felt like mistimed or confused shifts, but it was way better. And I hate to admit it, but turning off grade braking actually works

[oneandzero]

I tried this today and it did appear to shift smoother but it was really hard to tell because of my tune. I am temped to go back to a regular shift to try out.

[Thomcat]

Funny they all say downhill grades but it sounds like some programming eff up because it is doing it on any grade. Probably the slight forward rake of the truck is tricking the computer!

Appears to be triggered by the pitch and yaw sensors built into the chassis displayed in the DIC graphic depicting the percentages and 2WD/AWD/4WD wheel indicator (not on by default in the info screen, but can be added from the display list). Mine shows 0% pitch and 0% yaw when driving on flat ground and extra grade braking as soon as the down angle exceeds 1%.

[andyhaug]

I have tried this in the past, but after reading this I gave it another shot. It does seem to help with braking, I do not have as much clunking with grade braking disabled. However when I downshift it still seems pretty clueless. If I am moving 15-20 mph, and let the transmission get to 4th, then go to about half throttle there is still quite a bit of delay and it will still double downshift. I would still rather have the 4L80E that I traded in to get this pos.

[jamin87ss]

Tried it on shirt rude hom last night, hurt is still out will drive more again today,

 

Question for u guys, why is grade braking not working when in tow haul mode? Is my truck screwed up? Or are they all like that? Seems that would be when u want it working

[O_J_Simpson]

Tried it on shirt rude hom last night, hurt is still out will drive more again today,

 

Question for u guys, why is grade braking not working when in tow haul mode? Is my truck screwed up? Or are they all like that? Seems that would be when u want it working

Were you leaving the bar?

[fondupot]

Been turning off grade brake assist all week. The trans def seems to respond better to WOT inputs. Where before It would hesitate and sometimes lug in too high a gear.

 

Still waiting to hear from Blackbear if it can be tuned out.

[Sir Dan]

2016 5.3 with 8 speed here. Not having regular clunking or really any strange shifting but I tried turning off the grade braking just to see. I didn't notice any change at all.

I would urge people here with clunking and shift rpm flare to try disconnecting the battery overnight to reset the TCM. It has worked many times for me with other vehicles to sort out trans issues. This would especially apply to anyone that installed a tune or had the fluid changed recently.

[No Tyme]

After reading this I had to try it on my 14 LT and sure enough after you release the Tow/Haul button you get a message that Grade Braking is disabled.

I only drove 20 miles, did a quick round trip and I did notice one thing: the truck seemed to want to light up the tires a bit easier...

I also noticed that shifting did seem a bit quicker but I need to drive under some differant conditions and a few more times before I am totally convinced. But first try I did see a differance, and for the better. MPG went up slightly.