Turning off Active Grade Braking

slowfive0 · August 6, 2016

I have 70,000 miles on my 2015 Sierra 1500 --- 6.2/8 spd Denali. It developed the clunking (typically on a decel at low speeds). Usually, notice it in heavy stop and go traffic or when rolling up to a light. It wasn't there new and got progressively worse as time went on. Had many trans reflashes, etc but didn't fix the problem. GM eventually came out with a technical service bulletin to address my concern and they replaced the transmission. I forget how long ago, but I think it was around 55,000-60,000 when I got it replaced. Problem free and no abnormal clunks since.

I do know that the problem was a stack up of clearances in one of the clutch packs in early build units. I know they corrected that (iirc mid 2015 builds and later). So obviously, later builds have updated clearances in the trans and as time goes on, calibrations are further refined to improve driving experience that much more.

Love my truck! GM has take care of my concerns and I'm looking forward to buying the new generation truck. Oh and for the record, my buddy bought a brand new 2015 F-150 with the 3.5 ecoboost and my truck is faster in the 1/4 and gets better economy to boot. I took my truck to the track to see what it would do and it went 13.77 at 99mph with a 1.93 60 foot stock! It went 14.0's in the heat! I weigh 295 to boot. Truck weighs 5700 without me. I've towed 7000lbs with it and it did it with ease. Towed through the mountains coming back from SC/GA area to MI. It had no problems running the speed limit with that weight even going up grades. Never felt like it was overworked one bit. Averaged 13-14 while towing that weight at 70-75mph. Great powertrain!

Economy is where I can't believe it. Over my last 10 tanks I've averaged 20-21mpg driving in mixed driving conditions. My average speed was 34 mph. One tank was in the 19's cuz I got a little wilder with my foot lol! My lifetime average up until 60,000 was around 18. That included some towing and tanks where I didn't care what the economy was. I screwed up and reset the trip odometer (truck has 2 of them) that I was keeping track of the lifetime mileage with. Since then, over 3000 miles, I'm averaging 19.5 at an average speed of 32 mph. Can't say enough good things about this truck/powertrain! An "A+" to you GM!!!!

NOTE: if you dog it and drive it like a vette the mpg drops lol! The key is not doing the jack rabbit starts. When I take off, I let it shift out of 1st around 2000 and then around 1700 for 2nd and so on. Progressively lower rpms for the next few gears as the truck gets up to speed. It isn't accelerating excessively slow where people get pissed and its not wasting excessive fuel. I have averaged 21.5 over a tank, but that is driving very carefully and probably pissing people off behind me. Again, this is mixed city driving----I'd say 50/50 split. On freeway, I get 21-22 at normal speed (70-75). If I keep it 65-70, it goes up in the 22-23 range.

Can you tell I like this truck :-D Imagine losing 600-700lbs! I'd say low 13's and at least 2 mpg better.....!

Good luck with your trans woes original poster. Hope GM does right by you. I'd say be nice but firm and be persistent! Good luck

David2015 · October 19, 2020

Why does my grade breaking activate under normal driving conditions? I can be driving on flat level surfaces and let on the gas pedal and the grade breaking activates. I will also note my cruise control does not work when this occurs. I have had in the shop they have installed new break pedal switch and correlated it to the correct position. Then all good for a couple days and now back doing the same thing.

Jimchev16 · November 4, 2021

Ok. I know how to turn off the Grade Brake function (holding the trailer button down for 5 sec) to avoid high RMPs when rolling downhill with a trailer load.. But if this is disengaged...does it still help avoid using the overdrive gear when riding the hwy? I do NOT want the overdrive on when pulling a heavy trailer, but must get rid of this annoying Grade Brake - down hill downshifting and burning up my engine at 4500RPM. I have a brake controller with trailer brakes I would rather use instead.

Avoid the overdrive gear when pulling a trailer, but at the same time be rid of the Grade Brake Function...?