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

fondupot · April 28, 2016

I tried this, jury is still out on whether it makes a difference or not.

I live in a flat area, so I have never seen the grade brake assist turn on before. But maybe it affects something in the background during normal driving that affects shifting and response time. Who knows.

I bet Blackbear can permanently disable it thru TCM tune.

Deanjo · April 28, 2016

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?

Or it could be that the grade braking simply isn't working as specified. It would not surprise me. I wonder if the guys that do the custom tunes have grade braking disabled by default which is why so many people claim better shifting even without changing the shift points after a tune.

OmniGLH · April 28, 2016

I tried this, jury is still out on whether it makes a difference or not.

I live in a flat area, so I have never seen the grade brake assist turn on before. But maybe it affects something in the background during normal driving that affects shifting and response time. Who knows.

I bet Blackbear can permanently disable it thru TCM tune.

I'm in the Chicago area too. I've only ever seen "grade braking active" or whatever when towing and getting on the brakes while heading down a hill (like an off-ramp).

The more I drive it, it *definitely* makes a difference. A lot less shift-busyness, no more clunking or odd shifts.

I left it enabled for a short trip I took yesterday and immediately felt the difference.

Seems like the shift program is likely different when you disable grade braking.

Also - when I dropped the truck off this morning I talked to the guys at the shop - seems that this suggestion was NOT out of the factory. The service manager there figured it out himself.

OmniGLH · April 28, 2016

Or it could be that the grade braking simply isn't working as specified. It would not surprise me.

This is my bet.

fondupot · April 28, 2016

I'm in the Chicago area too. I've only ever seen "grade braking active" or whatever when towing and getting on the brakes while heading down a hill (like an off-ramp).

The more I drive it, it *definitely* makes a difference. A lot less shift-busyness, no more clunking or odd shifts.

I left it enabled for a short trip I took yesterday and immediately felt the difference.

Seems like the shift program is likely different when you disable grade braking.

Also - when I dropped the truck off this morning I talked to the guys at the shop - seems that this suggestion was NOT out of the factory. The service manager there figured it out himself.

Where you at Jimbo?

OmniGLH · April 28, 2016

Where you at Jimbo?

I live in Huntley (SW McHenry County) but commute to the Loop everyday.

Truck is currently sitting at Haggerty GMC in Villa Park, those are the guys that seem to be in agreement with most of the folks here, that something is wrong with the stock programming.

Whereabouts are you?

fondupot · April 28, 2016

I live in Huntley (SW McHenry County) but commute to the Loop everyday.

Truck is currently sitting at Haggerty GMC in Villa Park, those are the guys that seem to be in agreement with most of the folks here, that something is wrong with the stock programming.

Whereabouts are you?

Sent you a PM.

caveat71 · April 28, 2016

Going to test this out today. I have a Range AFM Disabler and it alone seemed to improve shifting performance (I havent had a bone jarring tranny clunk in over a month) so I'm interested to see if turning off the grade braking gets this to a sweeter spot.

Dunc · April 28, 2016

Or it could be that the grade braking simply isn't working as specified. It would not surprise me.

This is exactly what I am thinking. I'm thinking it could be doing strange things in the background even when the DIC doesn't light up saying the grad brake thing is active. I feel like out of all the other options/theories in the past that the grade brake one makes the most sense as it would affect the transmission directly.

Also - when I dropped the truck off this morning I talked to the guys at the shop - seems that this suggestion was NOT out of the factory. The service manager there figured it out himself.

If this continues to provide positive results, that service manager needs a raise.

The Mad Veteran · April 28, 2016

Truck is currently sitting at Haggerty GMC in Villa Park, those are the guys that seem to be in agreement with most of the folks here, that something is wrong with the stock programming.

I wonder if we make a big enough stink about this they will kick out a recall for an update to fix this issue. At least that's wishful thinking form my end.

Jordan18 · April 28, 2016

I have a 2015 Sierra with 6.2L max towing package (3.42 rear 8 Speed) and I tried this out and immediately could feel a difference. It doesn't seem as eager to get through the gears and the shifting is not near as harsh. Pulling up to stops it doesn't feel like it's restricting/braking itself anymore.

Responsiveness feels about the same (mine always seem to be very responsive) but when you punch it holds the gears better when it's upshifting. I feels like my 2008 6 speed in regards to shifting.

Not sure about mileage, but if this "setting" really does make better use of the throttle then it might see gains. I even tried reproducing the "guaranteed clunk zone", which was tapping the throttle while doing about 35-40 mph, and it just held rpms instead of a very audible clunk because the transmission didn't know what to do.

OmniGLH · April 28, 2016

Ya know... I swear I noticed a slight improvement in average MPG's on the DIC too.

Dunc · April 28, 2016

Ya know... I swear I noticed a slight improvement in average MPG's on the DIC too.

Hmm I'll have to check mine as well...but this would again make sense to me as the trans isn't being hold to slow you down anymore with the feature off.

IROCTHlS · April 28, 2016

Interesting! I'll have to keep this in mind when my truck is finally delivered. It's king of weird they would have this activated at all time and sounds like they need to fix this. Maybe they will post a recall and update the software later on to have this turned off when you get in and activate it when you want.... how it should be.

Edit:

Anyone have the same issue with the 2016 6 speed?

i have the same issues on the 2016 silverado.. havent tried turning it off though but will give it a try and see if it helps.

sk · April 28, 2016

Great find!!

I have been wondering about this too. I'm going to disable it tonight and drive it for a few days to see if the shift issues improve (as long as I can remember to disable it each time I start the truck ).

It makes sense that MPG's would improve with this disabled. When it is turned on and you let your foot off the gas and coast the grade braking may be kicking in (but it's not supposed to do this unless you are on a downward incline). When you go to give it gas it takes more effort to get the truck back up to speed and because of this you probably spend more time in V8 mode. With the grade braking disabled I would expect the truck to spend more time in V4 mode so your mileage should improve.