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8 speed suddenly went out. No forward or reverse gears

kgkern01

By kgkern01
in Engines & Drivetrain

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kgkern01 Enthusiast

kgkern01

Posted
Posted

Of course this happened exactly 1 year after the warranty expired.  I accelerated and then it just lost forward gear like I had put it in neutral.  No forward, reverse, and doesn’t even feel like I’m switching it into Drive or Reverse when it’s running.  Before the warranty went out I had taken it in regarding the delayed cold engagement issue, but the dealership said they could reproduce it of course ?.  So, any suggestions or ideas what could have happened to just lose all forward and reverse gears in this 8-speed?

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flyingfool
flyingfool

i would try the popular Camaro Forums it might have more members that have done the research already on 8-10 speed upgrades repairs etc.. those guys might be more performance and hands on than most me

M1ck3y
M1ck3y

Can someone else chime in? Did that go right over his head or am I missing something?

flyingfool Senior Enthusiast

flyingfool

Posted
Posted (edited)

check for any known TSB's 8 speeds have tech  issues in software and i'm sure a pro shop knows whats up.  call Precision Transmission in TX  he might might know where to point you to. he does quality work but i think he's only into older transmission. 806) 372-2210

 

also a tuner might be able to reflash it , and do a recal on it and purge cycle. this might work, GM dealer might be able to do this too

Edited by flyingfool
kgkern01 Enthusiast

kgkern01

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I don’t think a tune or reflash is going to make drive/reverse start working again though, it has to be a physical issue to cause it to go out like that.

YYC-SIERRA Enthusiast

YYC-SIERRA

Posted
Posted
3 hours ago, kgkern01 said:

No I didn’t, but I had the dealership do a flush last summer.

Fire it up, put in neutral, and check the fluid level, is it normal?

kgkern01 Enthusiast

kgkern01

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14 minutes ago, YYC-SIERRA said:

Fire it up, put in neutral, and check the fluid level, is it normal?

Since there is no dipstick on the 8-speed, and the fill plug is in the oil pan, I just easily check the fluid.  However I’ve had zero leaks in this truck, and underneath it has no oil at all, very clean, I’d assume it isn’t a low fluid level.  The transmission temp when it went out was not hot either, maybe 190?

mjm-1957 Enthusiast

mjm-1957

Posted
Posted

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.

kgkern01 Enthusiast

kgkern01

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4 minutes 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.

If you’re the transmission guy at a GM dealer, any suggestions or ideas as to what could have happened?  I had always gotten a slight whine when I would accelerate hard too, other than the above issue of the delayed cold engagement.  I just want to get an idea of what could have gone out and what I’m looking at for a repair?  Thanks :)

mjm-1957 Enthusiast

mjm-1957

Posted
Posted

I would be looking for a loss of hydraulic pressure like a pump failure or a catastrophic mechanical failure.Any noises while running in gear and not moving?

kgkern01 Enthusiast

kgkern01

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12 minutes ago, mjm-1957 said:

I would be looking for a loss of hydraulic pressure like a pump failure or a catastrophic mechanical failure.Any noises while running in gear and not moving?

No noises, when I put it in gear it does nothing, sounds exactly like neutral.

mjm-1957 Enthusiast

mjm-1957

Posted
Posted

You of course slid under there and made sure the shift cable and lever are still in one piece and attached I am assuming?

JimCost2014 Senior Enthusiast

JimCost2014

Posted
Posted
45 minutes ago, kgkern01 said:

Since there is no dipstick on the 8-speed, and the fill plug is in the oil pan, I just easily check the fluid.  However I’ve had zero leaks in this truck, and underneath it has no oil at all, very clean, I’d assume it isn’t a low fluid level.  The transmission temp when it went out was not hot either, maybe 190?

CEL on?

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