8 speed suddenly went out. No forward or reverse gears

kgkern01 · November 27, 2020

4 minutes ago, mjm-1957 said:

Does the shift quadrant follow the shifter movements and is there any check engine light on?

Yeah, the gauge moves between all of the shifter positions correctly, and from what I could see of the shift cable it still appeared to be intact and connected. I was passing someone when it just went out.

mjm-1957 · November 27, 2020

Powertrain is 5years -100,000 miles on a 2015. What is your delivery date? Any extended warranty?

mjm-1957 · November 27, 2020

Give me the last eight of the vin and ill run it to see if you have any warranty left.

kgkern01 · November 27, 2020

50 minutes ago, mjm-1957 said:

Powertrain is 5years -100,000 miles on a 2015. What is your delivery date? Any extended warranty?

The warranty expired Nov 18, 2019 I believe. I took it in for the delayed cold engagement issue the last week it was under warranty, and of course they said they couldn’t reproduce it, even though it happens every time I first started it when cold out in the morning.

M1ck3y · November 27, 2020

52 minutes ago, kgkern01 said:

The warranty expired Nov 18, 2019 I believe. I took it in for the delayed cold engagement issue the last week it was under warranty, and of course they said they couldn’t reproduce it, even though it happens every time I first started it when cold out in the morning.

Yeah they pick and choose what they feel like. Most times you'll get the cannot not duplicate because the problem isn't bad enough yet.

Have you tried giving it throttle? Does it rev freely like it would in park/neutral or does it sound feel like there's load on it. If it sounds like there's some load on it, its probably just not engaging.. at all. If you rev it enough it will engage so be careful.

That happened to me the day after I got my brand new truck. I was so pissed off I started giving it some pretty good throttle (maybe 2500), then it engaged. No idea if/what I broke but it hasn't done it since.

Edited November 27, 2020 by M1ck3y

kgkern01 · November 27, 2020

It revs freely as if it were in neutral, even lets it go up to 5k freely.

flyingfool · November 27, 2020

5 hours ago, mjm-1957 said:

Even if you unplugged the wiring harness you would still have reverse and one forward gear as a failsafe. That 8 speed transmission is a huge piece of ****** and has been trouble from the start in 2014. I am the transmission guy at a Buick- GMC dealer and can't believe that GM released this trash and can't come up with any fixes for it. I spend most of my time trying to fix the unfixable, harsh downshifts, flares on up shifts, delayed engagement and of course the TCC shudder.Absolute garbage, they should make a retrofit kit to slip a 4L80 in instead.

You can actually. Goat Rope Garage showed how to install a Camaro with manual transmission software into your 8 speed truck. and run a built 4L80

silveradosid · November 27, 2020

is it a wheel drive, possibly the transfercase has slipped into neutral

kgkern01 · November 27, 2020

Yes it’s 4WD, but putting it into Park does engage the parking lock in the trans, and if the transfer case was in neutral it would still roll.

Side hypothetical question, if the 10-speed is that much better of a trans than the 8-speed, can the 10-speed be swapped out, if the worse case scenario happens where I need a whole new trans that is?

M1ck3y · November 27, 2020

2 hours ago, kgkern01 said:

Yes it’s 4WD, but putting it into Park does engage the parking lock in the trans, and if the transfer case was in neutral it would still roll.

Side hypothetical question, if the 10-speed is that much better of a trans than the 8-speed, can the 10-speed be swapped out, if the worse case scenario happens where I need a whole new trans that is?

I'm not sure if it can be swapped in. But the 10 speed isn't what I would call better. Dealerships apparently have more complaints about the 10 spd then the 8spd. Its just too many gears. The 8spd is a awesome transmission. But not until you put a different converter in and tune it.

kgkern01 · November 27, 2020

Ah ok, just a thought lol. So what is the average dealer price for swapping the whole trans, just to get a worse case scenario, in case it’s not just a bad converter or pump?

M1ck3y · November 28, 2020

2 hours ago, kgkern01 said:

Ah ok, just a thought lol. So what is the average dealer price for swapping the whole trans, just to get a worse case scenario, in case it’s not just a bad converter or pump?

Sorry no idea on cost. But if they don't offer it to you, make sure you push them for a discount. GM will usually give a reduced price to keep the customer happy. Or as happy as they can be, lol.

kgkern01 · November 28, 2020

37 minutes ago, M1ck3y said:

Sorry no idea on cost. But if they don't offer it to you, make sure you push them for a discount. GM will usually give a reduced price to keep the customer happy. Or as happy as they can be, lol.

I hope they give me a reduced price, especially since I had brought it in with transmission issues and a TSB when still in warranty and they gave me the “can’t reproduce” response .

flyingfool · November 29, 2020

why 10 speed? those things suck so much power because they weigh a Ton , so much more money for those too, I would fix what you got. I think going to a 4L80 mechanical or electronic is a better option,

Edited November 29, 2020 by flyingfool

kgkern01 · November 29, 2020

1 hour ago, flyingfool said:

why 10 speed? those things suck so much power because they weigh a Ton , so much more money for those too, I would fix what you got. I think going to a 4L80 mechanical or electronic is a better option,

I’m going to stay with the 8-speed, it was just a random thought. It goes to the dealership next week, so I’ll see what the diagnosis is then. If it is the torque converter is there an aftermarket option with similar stall speed as stock that is more reliable?