Jump to content

8 speed suddenly went out. No forward or reverse gears

kgkern01

By kgkern01
in Engines & Drivetrain

 Share

Recommended Posts

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?

  • Replies 44
  • Created
  • Last Reply

Top Posters In This Topic

Popular Days

Top Posters In This Topic

Popular Days

Popular Posts

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

Posted
  • Author
Posted

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

Posted
  • Author
Posted
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

Posted
  • Author
Posted
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

Posted
  • Author
Posted
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?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.4k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,760
    Total Members
    8,960
    Most Online
    MASONV88888888
    Newest Member
    MASONV88888888
    Joined

  • Who's Online   4 Members, 0 Anonymous, 1,131 Guests (See full list)

  • Latest Articles

  • Posts

    • MASONV88888888
      Another 6.2L engine failure!

      By MASONV88888888 · Posted

      My 2025 Silverado 1500 had to receive a brand-new engine (long block) under warranty last month at only around 16,500 miles. Before the replacement, the truck repeatedly displayed "Engine Oil Level Low" warnings, even though the Oil Life Monitor still showed around 50% remaining after about 6,000 miles since my last oil change. After seeing the warning several times, I checked the dipstick with the engine cold, and the oil level was completely normal. The next day, the message escalated to "Add Engine Oil." At first, I assumed it was just a faulty oil level sensor, so I brought the truck to the dealership. After inspecting the engine, they found internal cylinder wall scoring and ultimately replaced the entire long block under warranty. Before this happened, I was planning to install a 4-inch lift and suspension upgrade on my truck. After needing a new engine at just 16,500 miles, I honestly don't see the point anymore. I also contacted GM to ask whether my vehicle qualified for a buyback, but I was informed that it does not at this time. Anyway, this experience has left me with serious concerns about the long-term reliability of this engine. I sincerely hope NHTSA expands the current investigation or recall to include 2025 model and performs a thorough inspection of affected vehicles. My biggest concern is that these engines may fail shortly after the powertrain warranty expires. If GM truly stands behind this engine, then at the very least, please consider extending the powertrain warranty to 10 years for affected owners. That would go a long way toward restoring customer confidence.
    • Grumpy Bear
      OCI, not when but why?

      By Grumpy Bear · Posted

      Without exception but then I'm the odd duck, right? I know what goes into that test, how it is calculated and thus how to beat it. But EPA values are often not beaten by the general public and the government has in past years adjusted the means and methods to come to those values to more closely approximate "Joe Average".    The only real trick to beating that EPA average is don't drive like "Joe Average".    It's the same method you used to profit from "Economic Migration" and in doing so beat the 'stats'. But you, like me, are not "Joe Average".     The thing you don't seem to grasp is this "Purchasing Power Index" isn't forward looking. It doesn't predict what it going to be but looks backward and states what it was. They are not telling us what the THINK, they are telling us what they MEASURED. Example:    Wife says "I'm going to lose 40 pounds by Christmas". May she does, maybe she doesn't but the doctors office who weighed her when she made that statement and again at Christmas only REPORTS what the RESULT was. You and I can banter about what was possible and what aunt Tilly did till the cows come home but the result is the result. Arguing otherwise is.....irrational. That's all I'm saying. This isn't about:      What you are calling a 'Statistic' is a RESULT not a CALCUATION and as a result the RULE. Like gravity as a rule, it can not be broken. 
    • MASONV88888888
      Rattle in the rear!

      By MASONV88888888 · Posted

      Just wanted to say thank you for posting this. Years later, your thread is still helping Silverado owners.   I bought my 2025 Silverado 1500 in January 2025, and I've had what feels like the exact same rattle since day one. After reading your findings, I believe my truck has the same issue with the cable carrier contacting the rear sliding window. To be honest, I had pretty much given up on pursuing the issue. It wasn't until I recently drove another brand's pickup that I realized just how quiet their cabin was—and how noisy mine has been all along. On my truck, the rattle happens on almost any paved road, gets even worse on rougher pavement, and I can even hear it during braking and acceleration.   I actually referenced your thread when submitting my case to GM, hoping they'll recognize this as a recurring issue instead of treating it as an isolated incident. The reason I reached out to GM first is because my dealership told me they would need to keep the truck for at least two days just to diagnose the problem. I was concerned that even after two days, they still might not be able to identify the source of the rattle before giving the truck back to me. I had also asked a few dealerships about this issue during previous service visits, but none of them seemed to know what was causing it or had a solution. That's why I decided to contact GM directly first, hoping they might already have an official repair procedure or guidance for this issue.   I also hope GM eventually comes up with an official fix for this problem. I have a feeling there are many Silverado owners experiencing the same rattle, but most either choose to live with it or simply don't know what the cause is.   Really appreciate you taking the time to document your diagnosis. Your post is still making a difference years later.
    • Buckwild27
      Gas Prices

      By Buckwild27 · Posted

      I have 2 choices. 
    • Grumpy Bear
      Gas Prices

      By Grumpy Bear · Posted

      Do you have access to BP fuels? Some stations have Silver 91 E-0 priced the same as their 93 E-10.  There is a local Marathon with 90 alky free for $6 a gallon but I go down the road to BP for $5-ish. They also have a 100 E-0 but that stuff is $10 a pop. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...