shifting issues

Riki Knight · June 13, 2018

So I am currently on vacation 300 miles from home. My truck is a 16 1500 Z71 and has about 33000 miles on it and all of the sudden driving on a flat surface grade braking will enable. The truck is also shifting randomly and violently. Sometimes when making turns in auto mode it will feel as though the 4wd system is engaged. Anyone else encounter these issues? Anyone might know what could wrong that I can fix real quick while I'm away?

rudyb · June 15, 2018

Sorry to hear about your situation! I haven't experienced the grade braking engaging unexpectedly, but my transmission definitely acts up. It seems to be linked to my driving style. If I grandpa around drive the truck easy like I want it to last 15 years, it shifts like dog crap.

Example: One road I travel home is 40mph speed limit. I let off the gas for a red light up ahead, truck speed slows to 32-35mph, light turns green so I press my foot into the pedal just slightly as if I wanted to gradually speed back up to speed limit. The trans will downshift violently and whip your neck. It seems to happen randomly at other times, but mostly 30-45 mph and around downshifts.

In contrast, if I drive it like a race car (100% throttle leaving corners or red lights, 100% braking into corners or stops) it shifts just magically and it's quite pleasing. It flows from gear to gear, smooth as butter. Never a shortage in power, keeping you sucked back in your seat.

I can't help but wonder if they tailored the transmission design to that majority of ass-hat drivers that we all see everyday. It's a shame too because that's not how I want to drive at all. I'm mostly over here trying to beat my high score fuel mileage. I did 10 under on a 5hr drive a while back and averaged 27.2mpg. The only way to beat it is to grandpa around and I don't think this pickup was made for that. Oh, I also have a 2016 Silverado 1500 6-speed. 4WD double cab LT.

Riki Knight · June 15, 2018

Thanks for the reply. I do notice that the truck drives better when I drive it mad. I'm going to take it to the shop when I get back home. Yesterday it acted just fine... it's really weird. How did you manage 27mpg?! At best I get 19 on our 5 hour trip each year.

Supreme Pizza · June 16, 2018

Disconnect the battery for 30 minutes. That will reset all the computer stuff, so that it will at least get ya home (hopefully).

Jaychevy81 · June 16, 2018

I will def say the same if I drive it like I stole it it runs through the gears like it should. If I drive like driving miss daisy lol it’s like riding a mechanical Bull lolol.

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Riki Knight · June 17, 2018

Update for anyone with similar issues. We made it home safely but had a few more issues. I have resorted to turning off the grade braking manually by holding down the trailer button for a few seconds. I took it out of auto and stayed in 2wd mode, still turning like 4wd is engaged. Cruse control decided to automatically turn off on me randomly and also didn't work for 1/2 the trip.

Thanks everybody for the replys. I did not reset the computer as I want all the info there when the dealer looks at it, i dont think they will see anything though as I'm not putting out a CEL. I will be calling my dealership tomorrow. I just cant believe at 30000 miles this truck that i baby is going to crap...

Riki Knight · June 22, 2018

Update... took the truck in Wednesday and they replaced the MAF sensors. Drove it around for a bit and work like I just drove it off the lot.

Today it started grade braking again... back to the shop I go...

Chris75 · September 12, 2018

Just had this happen on my 2016 after getting it back from the dealership.

Truck is wildly downshifting, even around 70 MPH.

Cruise no longer works either.

Riki Knight · September 12, 2018

Chris,

They ended up having to replace my ECU after the 5th time taking it to the dealership and contacting GM. Has been fine since then, knock on wood.

Have them check the brake sensor and all the connections. One of the issues was my brake pedal was showing as depressed in the ECU when I was not pressing it. The voltage was off and anytime they moved the harness it would send a brake signal.

I hope this helps. Sorry I haven't updated this post but it took over a month to finally get it fixed.

Chris75 · September 13, 2018

Riki,

Makes sense, they had just replaced my brake booster. The pedal would squeak and had a mild pulsation when depressing.

So, my guess is the brake sensor was affected in the process of changing out the brake booster. I printed off your response when I took it back today.

Good fun going 70 and have the truck jam down into 2nd or 3rd on an L.A. freeway.