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

[Payton34]

Wow I cannot believe how much the grade braking effects the driving characteristics of the truck. I disabled today and cannot believe the improvement. It make no sense to me why GM defaults the truck to use grade braking. It should a selectable feature in the settings to keep on or off. I would assume it takes some wear off the brakes but I would think mileage would be hurt more since the truck isn't able to coast.

[The Mad Veteran]

Has anyone reported this to GM or started a petition that they change this asap? It sounds like this is an issue and that everyone is getting the results they want out of disabling it. They need to kick out a recall to set it so you can turn it on if you want it or not, not be on at all times. Give us the option GM!!

[OmniGLH]

Well... recalls are only for safety or emissions reasons. You'll never see a recall for a convenience issue.

 

They might issue a service bulletin and software update, but never a recall.

[Sean Demura]

So I found a company that does custom BCM tuning.

 

http://www.whiteautoandmedia.com/index.php?option=com_contact&view=contact&id=1&Itemid=56

 

I sent them a message about this, and they replied and said "It could be possible, but we would need a vehicle to test it on for a few days."

 

From the looks of their website they are located in Macomb, Michigan.

 

Any members live close by and willing to be the guinea pig??

 

If only I didn't have to risk voiding my warranty...

[The Mad Veteran]

Well... recalls are only for safety or emissions reasons. You'll never see a recall for a convenience issue.

 

They might issue a service bulletin and software update, but never a recall.

 

That's what I meant, not recall.

[pickmeup]

IMO GM has got it backwards. It should be off always unless you demand it on. Short of being in hilly or mountain roads there is no need for it because it hinders how sweet the 6 shifts without it.

[15chevy2015]

I hope Chevy/GM. Addresses this I also can tell difference with improved shift patterns with Grade disabled! 2015 Chevy 1500 CC 5.3 6 spd

[No Tyme]

I hope Chevy/GM. Addresses this I also can tell difference with improved shift patterns with Grade disabled! 2015 Chevy 1500 CC 5.3 6 spd

A couple of pages back someone posted contact information for GM. I called and created a"Service Request" for this issue. I suggest that others do the same if they want GM to take a look at re-programing the BCM.

[Bonker]

A couple of pages back someone posted contact information for GM. I called and created a"Service Request" for this issue. I suggest that others do the same if they want GM to take a look at re-programing the BCM.

 

I also created a service request. If everybody does this we may see some action from GM. More people need to get on the train.

[scottl1346]

stopped turning grade braking off today and my clunking has gotten worse now its doing it when letting off the throttle im getting a surge and a clunk and when shifting almost anytime if i knew of these issues when looking at these trucks i woulda stayed with my 96 blazer sounds and drives better then the 2015 junk.

[Thomcat]

 

Thanks for that info.. What is even more weird is that when I disabled it (at least the DIC said "Grade Braking Disabled" I noticed immediately when I left of the gas the truck wants to roll a lot easier. Before it would almost seem like the truck would slow down on its own. Now it just rolls forward without any restriction.. as in I have to press the brake harder..

 

It may just be me thinking this and my mind is playing tricks on me, but it does seem different to me. Placebo effect maybe?

Here's my 2 cents opinion on this matter for what it's worth.......after owning the '13 Avalanche w/ 6 spd. tranny I first encountered their new automatically engaging Grade Braking feature (DIC message) which engaged as a function of both vehicle angle and driver braking as well as another Trailer Anti-Sway assist (no DIC message) which automatically activated when the tow/haul button was pushed. I'm assuming these features were being piloted for the post '14 lineup of revamped trucks.

 

Appears that the Silverado has one normal and two distinct load braking modes which affect shift points and tranny behavior related to the firmness of shifts. The moderate grade braking mode (1) is on by default, likely GM assumes you are using a pickup truck for what it was designed i.e. to carry a heavy load and uses the tranny to give you additional braking, might even be a CYA to address potential lawsuits relative to stopping power.

 

If you press the tow/haul button for a few seconds and release the load braking, the truck will coast a lot longer/further and it will shift more smoothly like a car or SUV. An engine restart will put it back into grade braking mode 1. Likely a reason it is on by default.......e.g. if you actively defeat the assist and smash up a loaded truck and then attempt to blame the truck's brake design, GM could cite contributory negligence.

 

Seems there is an additional grade braking mode (2) not directly controlled by the operator (operates like the ones in the '13 Avalanche) that measures the angle of the downgrade and when the angle exceeds x AND the operator has been riding the brake for about 15-20 seconds to maintain a constant speed or prevent a runaway it will automatically shift to a more severe grade braking mode 2 (the DIC will indicate Grade Braking On) which will disengage automatically when the driver releases the brake or the vehicle reaches fairly flat ground (the DIC message will disappear) and the vehicle will revert to whatever mode it was in before whether grade braking disengaged or normal grade braking.

[SILVER SLED]

I tried this over the weekend on a 110 mile round trip. I topped my old best of 28.1 for 25 miles to 28.3 on a detour that I had to stop eight times on a 55 mile trip back. My 50 mile best went from 26.0 to 27.5. This rout is to/from the lake, so I drive it quiet a bit in the summer. I can't wait to try it again with the regular route where I got the previous 28.1 best.

[sk]

Okay update:

 

I previously posted that this did not make much difference for me. Over the past 4 days I have been turning it off every single time I start the truck and before I put it in gear. I changed my mind -- I am now noticing a slight improvement. My shifting wasn't too bad before except for the "clunk" that everybody is getting. The last few days the clunking has definitely decreased.

 

Sounds like GM needs to revisit the software calibration ...

[fondupot]

I've noticed a marked increase in gas mileage too along with the better behaving and less clunking from the trans.

[morrislee]

after about 2 weeks of driving without grade braking (disabling every time.......) I can say the clunk is gone, most of the downshift hesitation has been minimized. fuel economy does not seem to be any better, but it it still about the same. getting 12.6 to 12.7 L/100km (~22mpg) using both in the dash and calculation from pump.

 

Need a way to disable this outright, trying to find a guy with tech2 that can program this out or disable it by default.