2017 GMC Sierra 1500 2WD 6 speed transmission failure

[flyingfool]

6 hours ago, tlaw91 said:

TC lockup percentage will stay the same.

If you graph slip speed you can see it but we use the PICOscope and measure vibrations then based on the T vibration determine shudder

However you don’t feel it really so people don’t come in for it. They come in because transmission no worky


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any specifics of what to look for on the slip speed graph ?

[08 GMC]

Anyone reasonable in Dallas/Arlington area?

[flyingfool]

some more info on fixing the TechM switch films and installing transgo parts..

 

[2018GMC]

On 5/25/2020 at 8:52 AM, tlaw91 said:

Torque converter shudders

Causes the pump vane to shudder and dig into the case

Causes medal to go everywhere

Needs converter, torque converter housing, pump, valve body, techm, filter usually some steels and fibers, normally the 1-2-3-4 and 3-5-R clutches.

I just get the 1-2-3-4 clutch assembly because it’s already built and I’m the laziest.

Now you know!


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I assume there are a lot more 6l80 out there compared to 8l90.

I thought the 6-speed was the reliable trans vs the 8-speed?

 

Does the 8-speed suffer from this issue? Mine still has the factory fluid (only 11k miles on my 2018 8l90). Shifts fine most of the time but occasional lurch during cold start and clunky cold shifts. 

[tlaw91]

I assume there are a lot more 6l80 out there compared to 8l90.
I thought the 6-speed was the reliable trans vs the 8-speed?
 
Does the 8-speed suffer from this issue? Mine still has the factory fluid (only 11k miles on my 2018 8l90). Shifts fine most of the time but occasional lurch during cold start and clunky cold shifts. 

Contrary to popular belief, here’s the real scoop on these transmissions.

8 speed- shift like a teenage girl driving stick. Highly durable. Will not fail. Just feels like it is.

6 speed- 100k replacement interval.


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[flyingfool]

8 speed wont fail but the poor QC on the Torque Converter manufactuering says otherwise for both 6 and 8 speeds, high operating temps dont help either

[08 GMC]

15 hours ago, 2018GMC said:

I assume there are a lot more 6l80 out there compared to 8l90.

I thought the 6-speed was the reliable trans vs the 8-speed?

 

Does the 8-speed suffer from this issue? Mine still has the factory fluid (only 11k miles on my 2018 8l90). Shifts fine most of the time but occasional lurch during cold start and clunky cold shifts. 

My 2016 Denali would lurch when cold and when you slowed down for a stop sign, it would bang into gear pushing you forward like you were hit from behind. 8 speed.  GM dealer said there was no problem with it..

 

[flyingfool]

you should data log the trans while exhibiting this condition. 

[Locom0tive]

On 5/30/2020 at 1:38 AM, tlaw91 said:

Contrary to popular belief, here’s the real scoop on these transmissions.

8 speed- shift like a teenage girl driving stick. Highly durable. Will not fail. Just feels like it is.

6 speed- 100k replacement interval.


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If these are the same 8 speeds on the Canyons, I've seen the opposite around here. No one here gets to drive above 45 and all short trips so that doesn't help either. They're also a complete B**** to work on the other trucks.

[mojohn]

2017 Silverado LT. 6 speed trans.  39,000 miles. "Chevy shake" since @38,000 miles. Felt like suspension trouble to me, but 10 new Michelin tires didn't fix it.  Dealer says it needs a new torque converter. New one going in it in the morning. More information later.

[mojohn]

New torque converter was installed. No results to report yet. 

 

Stop and go traffic driving scheduled for June 24, this is when the shimmy is most noticeable, 1-12 mph.

 

*Dealer disconnects the battery overnight  during repair, so keep that in mind! 

I cannot recommend getting a state inspection on the way home from the dealer.  Code reader noted five monitors that displayed "not ready".    Failed inspection. 

Inspector instructions  were to drive it a few days and bring it back for re-inspection. 

 

More information later.

[jbman]

What is best Trans Fluid to use on 2018 Silverado 6 speed ? It has 42000  and should it be changed at this time? Thanks in advance

[mojohn]

On 6/20/2020 at 10:40 AM, mojohn said:

New torque converter was installed. No results to report yet. 

 

Stop and go traffic driving scheduled for June 24, this is when the shimmy is most noticeable, 1-12 mph.

 

*Dealer disconnects the battery overnight  during repair, so keep that in mind! 

I cannot recommend getting a state inspection on the way home from the dealer.  Code reader noted five monitors that displayed "not ready".    Failed inspection. 

Inspector instructions  were to drive it a few days and bring it back for re-inspection. 

 

More information later.

Drove it some at morning rush hour speeds (1-14mph). Shimmy/Wobble still exists. Vibrations at 25mph, 43mph, and 60+ are gone. I Guess the next stop is the drive shaft. I asked my service writer if they put in a better torque converter, or one just like the original, and he said it is same as the original. I asked if I'd have to replace it in 38,000 miles like the first one, and he said probably. I asked if changing ATF at 10,000-15,000 miles is recommended, and he said no.  

 

 

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6/15/2020: 2017 Silverado LT. 6 speed trans.  39,000 miles. "Chevy shake" since @38,000 miles. Felt like suspension trouble to me, but 10 new Michelin tires didn't fix it.

[flyingfool]

aftermarket torque converter from a reputable builder would make more sense...  but atleast you established the vibrations are gone at certain speeds. one guy on here installed a OEM converter from the Camaro zl1 . it has maybe 800-1000rmp more stallbuilt into it, and can handle more power