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

BIGDOGx · May 4, 2016

UPDATE FROM BLACKBEAR PERFORMANCE:

Ladies and dudes, unfortunately, the Grade Brake Assist feature is controlled by the BCM, and NOT the TCM.

Strange....but I guess we need to figure out who can tune the BCM to disable this by default.

Anyone have ideas?

Yes GM should fix this!

The Mad Veteran · May 4, 2016

Yes GM should fix this!

What he said!

I don't even have my truck yet and this pisses me off. lol

f8l vnm · May 4, 2016

My 2014 Sierra with the 6.2 L engine and six speed clunked and shifted horribly. My 2016 8 speed seems to not be as confused although sometimes it does clunk and also in slow stop and go sometimes it jolts. I have now put 50 miles using this method and I'll be damned it seems like it's really helping. I have now put 50 miles using this method and I'll be damned it seems like it's really helping I guess time will tell when I put more mileage. Thanks again to the op

redwngr · May 5, 2016

I don´t understand the guys that say their truck does not coast. Mine takes off like a missile down hill if I´m not riding the brakes . Even after the grade braking activates it has to downshift clear to 2nd gear to hold the truck back . Once you step on the gas pedal its back to normal . At least there´s no evidence of grade braking being active till I ride the brakes again ....Don´t know who´s right but I think if my truck was downshifting or would not coast to a stop all the time . I would visit my dealer ....Grade braking should only activate after you have been riding the brakes . Check the link below .

http://www.acdelcotechconnect.com/pdf/TechConnect_SepOct_2013.pdf

If the others are correct in their observations, grade braking must be doing something in the background whenever it is enabled, even if it does not 'engage'.

The first time it 'engages' in an engine cycle, it is supposed to give a message -- and there is no mistaking that the truck is doing something different when it engages.

I've tried the disable process on the 8 speed, and it gives the 'disabled' message, the same as on the 6 speed. (even though the OM makes not mention of whether the 8 speed can be disabled or not.)

So far I only have a few miles on it so will continue to try it before offering an opinion on any effect form being enabled, even if not engaged. .

BIGDOGx · May 5, 2016

If the others are correct in their observations, grade braking must be doing something in the background whenever it is enabled, even if it does not 'engage'.

The first time it 'engages' in an engine cycle, it is supposed to give a message -- and there is no mistaking that the truck is doing something different when it engages.

I've tried the disable process on the 8 speed, and it gives the 'disabled' message, the same as on the 6 speed. (even though the OM makes not mention of whether the 8 speed can be disabled or not.)

So far I only have a few miles on it so will continue to try it before offering an opinion on any effect form being enabled, even if not engaged. .

The problem as i see it, indeed it does activate as you said while pressing on the brakes for more then a couple seconds. The major problem imo is that either their timing for it to activate or how it activates is the issue here. It should not come on at all on a flat grade surface and it does so nearly coming to every stop light or traffic slow down. I like to gradually stop and not slam on my brakes for every light or slow down so riding the brakes is done so more then just on steep grades. It is simply just a half arsed programming and it needs to be disabled because chances of them actually fixing it to work as it is intended is lets face it not going to happen.

As a customer i don't think it is asking much at all for them to disable this feature as default and make customers wanting it on to press a button to engage it! Why it was not like that from the start of this feature many years ago is beyond me, i guess some engineers just lack common sense!

The Mad Veteran · May 5, 2016

i guess some engineers just lack common sense!

This!

Common sense isn't so common anymore and to me, it's a super power now!

wulfgott · May 5, 2016

Well, after a couple hundred miles commuting, some stop and go traffic, a couple jaunts up and through a local canyon on the way home from work. I like the way my truck drives FAR BETTER with it turned off. Considerably smoother shifting overall. Still a couple rough ones from stops but nothing even remotely close to the way it felt before. As for MPG, my average commute for work put me at 15.6 normally or round about, two days in a row now it has been at 17.9 since driving with it turned off. Of course, your mileage may vary and 2 days isn't really enough to tell with any absolute certainty. I for one will continue turning it off if I can remember to do so.

I HOPE GM looks into this to see if something is really working as intended or going on in the code as an unintended side effect causing the problems people have experienced with the shifting.

14silverado4.3 · May 5, 2016

These vehicles are engineered by morons, shitty AFM vibration, driveline vibes, grade braking issues, clunky trans., torque converter shutters, oil consumption, catch can delete, carbon buildup, God knows what other bullshit

I would be surprised if Chevrolet will be able to say "longest lasting trucks on the road" anymore

Trucko20 · May 5, 2016

In spite of the reservations I listed earlier, I went ahead and tried this yesterday and this morning. I did notice a nice difference with the shifting. I never really hated the way the truck shifted in the first place; I just figured it took some getting used to. But I would get the wonky clunks from time to time, usually in predictable places in my usual commute. On my commute today, the absence of the clunks was conspicuous. As I approached those usual clunky spots on my ride, in the back of my mind I was like "heeere comes the clunk......" and then....nothing. Kinda nice!

kp52 · May 5, 2016

After a few days and a few hundred miles I can say with certainty, at least on my '15 5.3/A6/3.42 that turning off the grade braking is an improvement. The one thing i hated about this truck was the trans behavior, especially when it would get confused trying to make a lane change or trying to get out of the way in a hurry. It seemed like 30 seconds before the truck reacted.. And then the clunks. I can tell withing a mile of driving now if I didnt turn off the grade braking by the way the trans feels, luckily it can be turned on and off on the fly. My wife's Jeep has that annoying engine stop-start thing and I have to push a button to shut it off every time it restarts, so turning the grade braking off ever time isnt a big deal. Would sure be great if GM would do an update but I wouldnt hold my breath

fondupot · May 5, 2016

If I recall there is a member on here that does some BCM programming. Gotta find who it is.

BrianBrianBrian · May 5, 2016

Subscribed. There is certainly a difference with the GB off but can't really tell what exactly is different. I will say though the shifting feels a little more timely.

Sean Demura · May 5, 2016

Tried this out on my 4.3 4x4 and the difference is very noticeable.

Much smoother shifting all around and I there seems to be less lag when I hit the gas.

I was 'okay' with the trans before, but now it feels like a whole new truck!

pickmeup · May 5, 2016

For certain on my 15 sierra it made a nice improvement . Seems like with it off the tranny is never searching for the proper gear to be in. It does make the truck more pleasurable to drive IMO. Hopefully GM will have a updated tune or at least a delete option for owners that want it.