Does anyone have this 1-2 shift 'slip'?

robvas · September 23, 2015

It's hard to really see/hear it in the video, but on the very first shift of my truck in the morning, it gets stuck between 1st and 2nd, the truck won't accelerate, then it finally shifts and everything is normal. I should have gotten the tach in the video.

Not sure if it's 8-speed specific, I never had this issue with my 2014.

https://www.youtube.com/watch?v=kUB96IcLe1s

fondupot · September 23, 2015

mine doesnt slip, but the first 1-2 shift after sitting all night is usually a little "off" compared to normal warm operating. It's probably just the tranny getting warmed up.

Higgs Boson · September 23, 2015

sometimes it does a slow shift on the very first upshift of the day, but never again.

it always does it on the first shift after uploading a tune change.

it's not a slip. its a hesitation.

TxTruckMan · September 23, 2015

sometimes it does a slow shift on the very first upshift of the day, but never again.

it always does it on the first shift after uploading a tune change.

it's not a slip. its a hesitation.

Why?

Higgs Boson · September 23, 2015

Why?

probably just a weak spot in the calibration algorithm torque management model delivery outlining a discrepancy in driver demand and delivered torque through cold temp trans shift pressure/speed lookup.

or maybe the transmission is about to fall out?

Badass69 · September 24, 2015

The 6.2 8 speed I test drove a week or so ago did it. Leaving the dealer lot it was like the truck died... then picked up and carried on normally thereafter. It was a very noticeable hesitation. The truck had 15 miles on it lol.

Was hoping this stuff was isolated

... I am picking up a new 6.2 8 speed tomorrow... lol

Sent from my SM-G900W8 using Tapatalk

Higgs Boson · September 24, 2015

mine really only does it after I flash the ecm and all the trans adapt stuff gets reset.

TxTruckMan · September 25, 2015

Mine did this pretty hard this afternoon when I was leaving my house. I pulled out of the driveway, got on it pretty hard, and it shifted really weird - almost like I hit the brakes during the shift. Down the street at the next stop I tried again and it shifted normally.

Very strange.

Badass69 · September 26, 2015

Mine does it first shift cold... I don't really care as long as the Trans doesn't fall out of the truck from it doing it!

Sent from my SM-G900W8 using Tapatalk

Ron.s · September 26, 2015

My 2014 has done it 3 times in almost 2 years and when warm twice vs cold once. In my case it does slip, the RPM climbs at least 1000 maybe more before it shifts. The dealer tranny guy said not to worry, ha ha.

bboyce536 · September 26, 2015

My 1-2 shift has done this multiple times as well. This has really been the only disappointment I have with the 8 speed. Even wot 1-2 upshift it delays and hits the rev limiter on occasion. Really hoping tuning would clear this up.

Badass69 · September 27, 2015

Mine clunks at low speeds too but I am used to this as its pretty normal for gm to have crummy transmission tuning. I won't complain or worry about it and will get the truck tuned shortly. I might even play with what I can... I mean I do own hp and efilive afterall

Sent from my potato

USAFASME7 · September 28, 2015

I have a 2014 6-speed 5.3. Mine did it this morning for the first time, and I JUST passed 1,000 miles on the clock. I was driving in wet weather, about 2 miles from my house, went around a corner and it definitely felt like tranny slip not hesitation. It wasn't from 1st to 2nd, but probably 2nd to 3rd. And no, it wasn't tire spin in the rain either...kinda weird.

Higgs Boson · September 28, 2015

I have a 2014 6-speed 5.3. Mine did it this morning for the first time, and I JUST passed 1,000 miles on the clock. I was driving in wet weather, about 2 miles from my house, went around a corner and it definitely felt like tranny slip not hesitation. It wasn't from 1st to 2nd, but probably 2nd to 3rd. And no, it wasn't tire spin in the rain either...kinda weird.

The 6 speed is known to slip 2-3, that's a different issue.

n i c k · September 30, 2015

Not sure if this fixed the sluggish 1-2 shift, but I haven't felt it since they replaced a harness last week. It was recall #15396 (harsh shift when starting in cold temps). They dropped the transmission pan and replaced some type of harness in the valve body. It took them almost a month to get the harness shipped in. They also did recall 15304. Something to do with 4wd engaging during low temps and displaying a "service 4wd" message.