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

[wayles]

I have been turning off grade braking for about a month now. While it has helped, it has not cured the problem. I still occasionally get the flare shift, or the clunky downshift, and it still feels like something is holding the truck back a little. If I do a full throttle run to 60 every other day or so, it seems to bring the transmission back in line for a while, much like spanking your kid. However, it begins to backslide (just like a kid) after a day or so.

 

I still have my best shifting when I put it into tow/haul mode. I use that around town, and when I get on the highway, I switch it off.

 

Seems like a re-programming is in order from GM. I have had two Grand Cherokees with 8 speeds, and both shifted flawlessly. Maybe GM should talk to Chrysler and find out how they're doing it.

 

I am considering a tune, just not sure of the warranty issues. Will be talking to my dealer tomorrow about it. I have a great dealer, so I am hoping they will say to go ahead with it.

[tnchevy]

Just because your dealer gives you the "go ahead" does not mean squat when it comes to warranty repairs. They get paid by GM to do the repair and if GM does not go along with the repair then the dealer is stuck paying for said repair out of their own pocket which is not going to happen. Your choice it to get the tune and void your warranty or not get the tune. If the truck is shifting that bad then I would say screw the warranty and get the tune or trade for another brand of truck.

[MyakkaLivin]

I encourage everyone who has seen positive results by "disabling grade braking" to open a service request to show GM that this is NOT just a couple of guys complaining about their trucks. This should be a quick software fix, but remember that the squeaky wheel gets the grease.

To all who have had positive results when disabling the grade braking, I need to ask a question to determine if my "disabling" is working: When not disabled, I assume when coasting at (say) 60mph, your tach is following the transmission down through the gears (right?). But when the grade braking is disabled, does it still follow the transmission down or does it drop immediately after taking your foot off the gas peddle (kinda like shifting the tranny in to neutral)? On my '15/5.3/6sp I see absolutely no change! Appreciate hearing from you guys.

[Dunc]

A tune is the best way to fix your trannsmission issues. Mine started shifting flawlesssly after getting tuned, even with grade braking enabled. Come over to the dark side haha.

A tune is in my future, but I'm not doing anything until I install the turbo kit. Then I'll do the tuning.

[wurgs]

To all who have had positive results when disabling the grade braking, I need to ask a question to determine if my "disabling" is working: When not disabled, I assume when coasting at (say) 60mph, your tach is following the transmission down through the gears (right?). But when the grade braking is disabled, does it still follow the transmission down or does it drop immediately after taking your foot off the gas peddle (kinda like shifting the tranny in to neutral)? On my '15/5.3/6sp I see absolutely no change! Appreciate hearing from you guys.

I haven't paid attention to the rpms but the best way I can describe it is it feels like it's in neutral when I step off the gas. Coasts smoothly.

[No Tyme]

My personal opinion about getting GM to do a software update on this grade braking issue is this...

 

I just don't think we will get anywhere with GM. For those of you who can't disable grade braking each and every time you start your truck will need to find an outside solution to this issue. Someone posted earlier about it being in the software for the BCM and posted of a place in Michigan that might be able to hack it. I believe this will be the only solution... JMO

 

[MOhunter92]

Tried this out and it helped my 2016 8 speed out IMMENSELY. Down shifting from 2nd to 1st was so slow, it would clunk and shutter into 1st. Extremely annoying and even dangerous, it lags so much between those gears that if I slowed to turn onto a street with traffic approaching, it wouldn't down shift and then slam into 1st as it lagged trying to figure out what to do.

 

It's completely resolved with grade braking off. The transmission is perfect with it off, no clunk and seamless shifting up and down. This needs to be resolved. Grade braking shouldn't be permanently active, what a stupid choice GM made.

 

 

Sent from my treestand using Tapatalk

[20L8TSierra24]

My brother and I both have cc 5.3 6 speeds and it made a difference for us. From a stop, the shift pattern is similar but no more clunks when getting back into the gas after coasting which is nice.

[No Tyme]

Well almost 2 months now and no contact from my dealer about this Service Request I opened. I spoke with the service guy out at a car show and gave me the opinion that GM will need to do testing on this issue before they would make changes. He was not encouraging... So life goes on and Grade Braking disabling continues every timer I start my truck.

[andyhaug]

Anyone know where the tilt sensors are located? Can they be unplugged or are they inside of the body control module? I would hope unplugging the tilt would disable grade braking.

[No Tyme]

Well, I found out that my service request was closed... No contact from the dealer or GM, they just closed it.

 

I am NOT happy with this grade braking issue being defaulted to the on position and opened another service request today. The GM rep said my case will remain closed until they make a diagnosis on my truck. Well they have to contact me first to set up an appointment correct? I'll give them until Friday and then I will call them.

[szalkerous]

THANK YOU THANK YOU THANK YOU THANK YOU

 

Tried the "Grade Braking fix" on my 2015 Silverado CC LTZ w/ 6-speed. SO much better! Give that service manager the prize of the year!

[szalkerous]

Does anyone know if the "Grade Braking On At Startup" is something that can be tuned by an HP Tuner? I use one for my '99 Z28, and have some unused credits...

[winn0040]

Does anyone know if the "Grade Braking On At Startup" is something that can be tuned by an HP Tuner? I use one for my '99 Z28, and have some unused credits...

I think some guys have asked Blackbear about the possibility of getting it turned off by default, but I've just grown accustomed to holding the button for 4 seconds every time I start the truck. Well worth the time it takes I think!

 

On a side note, I love the look of the chrome grill on your 2LZ. Is that factory or an aftermarket insert? I would like to put one on my non-Z71 LTZ.

[No Tyme]

THANK YOU THANK YOU THANK YOU THANK YOU

 

Tried the "Grade Braking fix" on my 2015 Silverado CC LTZ w/ 6-speed. SO much better! Give that service manager the prize of the year!

My understanding that it is controlled by the BCM and I believe Black Bear cannot get into that, only the ECM and TCM. You must disable it every time you turn the key and start the engine. If you hold for 5 seconds it will turn off: hold another 5 seconds it will re-engage. This is something I believe should be "Disengaged" by default.

Currently have a service request which I hope to have GM take a look at this. I encourage others to open a service request if you feel this should be set to OFF by default.