16-NA-175 8 Speed Shudder UPDATE

[Abiker21]

10 hours ago, dwchapmanjr said:

Resurrecting the dead.  I had a P0711 earlier in the week with a P0700 (this caused the dash MIL).  Cleared it and only P0711 came back which doesn't cause the MIL.

Did they replace the temp sensor based on P0711 alone?  For P0700 and the dash check engine light to happen P0711 has to trigger two drive cycles.

What I did notice is my thermostat seems to be stuck open as transmission never gets up to temp like it used to.  Thermostat opens at about 192F I believe.

 

More related to this topic, I'm nearly 2 years out on my flush with the "new" fluid and no shudder but I do have rough shifts that I believe may be related to temperature or temp sensor.

They should be able to ohm out the harness to test it. It sounds like you have a bad harness. It will fix your shifting problem. 

[dwchapmanjr]

1 minute ago, Abiker21 said:

It will fix your shifting problem. 

Funny part is I just got used to the shifting.  I really think my thermostat is just broken/stuck open though.  Monday I got both codes which caused MIL, Tuesday a single instance of P0711 and then nothing since.

 

I get readings from the sensor so its returning data that seems normal.  Its highly variable but I think that's because the thermostat isn't closed and allowing it to warm up properly.  I thought this was a sensor or harness issue since most all P0711's seem to lead there but I think my case might be different.  Have an appointment Monday with my findings and let them figure out what to do with it.

 

What makes you think its the harness?

[Abiker21]

3 hours ago, dwchapmanjr said:

Funny part is I just got used to the shifting.  I really think my thermostat is just broken/stuck open though.  Monday I got both codes which caused MIL, Tuesday a single instance of P0711 and then nothing since.

 

I get readings from the sensor so its returning data that seems normal.  Its highly variable but I think that's because the thermostat isn't closed and allowing it to warm up properly.  I thought this was a sensor or harness issue since most all P0711's seem to lead there but I think my case might be different.  Have an appointment Monday with my findings and let them figure out what to do with it.

 

What makes you think its the harness?

At cold start is the tans temp accurate? Regardless,  purchasing a TCM online will be a lot cheaper than through a dealer. Then my next question is what made it go bad, a shorted harness? 

[dwchapmanjr]

2 minutes ago, Abiker21 said:

At cold start is the tans temp accurate? Regardless,  purchasing a TCM online will be a lot cheaper than through a dealer. Then my next question is what made it go bad, a shorted harness? 

Yes seems accurate and transmisson temps are in line with people who have done the thermostat delete. I have gm protection plan with $100 deductible so that's all I should be out of pocket. 

[Abiker21]

6 hours ago, dwchapmanjr said:

Yes seems accurate and transmisson temps are in line with people who have done the thermostat delete. I have gm protection plan with $100 deductible so that's all I should be out of pocket. 

Well shoot,  you're set. Please let us know what they find. Diagnosing this problem wrong can be a pain in the backside.

[dwchapmanjr]

5 hours ago, Abiker21 said:

Well shoot,  you're set.

From your persistence, I decided to fiddle with my scan tool a bit more and it captured a freeze frame on the most recent event.  It detected transmission temp at 48.2F and its the 3rd time out of the past 11 test cycles.  7 successes and 1 instance where no test was done(assuming aborted due to operating conditions).  Entirely possible it could be sensor or thermostat or both at this point.  Should be interesting to see what the dealer determines/finds.  I'm just hoping its a 2 piece harness being a 2015 which makes for an easier repair.  Not that I have to do the work but the less parts come off the less possibility for mistake since valve body has to come off on the 1 piece.

[Abiker21]

On 9/25/2020 at 10:29 AM, dwchapmanjr said:

From your persistence, I decided to fiddle with my scan tool a bit more and it captured a freeze frame on the most recent event.  It detected transmission temp at 48.2F and its the 3rd time out of the past 11 test cycles.  7 successes and 1 instance where no test was done(assuming aborted due to operating conditions).  Entirely possible it could be sensor or thermostat or both at this point.  Should be interesting to see what the dealer determines/finds.  I'm just hoping its a 2 piece harness being a 2015 which makes for an easier repair.  Not that I have to do the work but the less parts come off the less possibility for mistake since valve body has to come off on the 1 piece.

I have the 2015 as well, I'm assuming you have the 6.2? When mine was acting up, from a cold start I could watch the tans temp on the driver's display be erratic and even dash out. It should only increase not up and down. 

 

I had wheel hop with my 6.2 and adding the road master active suspension fixes it, but everyday driving overall makes the backend feel like the front when going over bumps/ curbs. Plus it helps with towing. 

[dwchapmanjr]

18 hours ago, Abiker21 said:

I have the 2015 as well, I'm assuming you have the 6.2? When mine was acting up, from a cold start I could watch the tans temp on the driver's display be erratic and even dash out. It should only increase not up and down. 

Yes, 6.2 as well.  GM/Chevy Protection plan just approved a new temp sensor.  Dealer read a -48F on it.  They're checking thermostat now so at the least the temp sensor is bad but approved under warranty.

18 hours ago, Abiker21 said:

I had wheel hop with my 6.2 and adding the road master active suspension fixes it, but everyday driving overall makes the backend feel like the front when going over bumps/ curbs. Plus it helps with towing. 

Interesting, I had to look up road master.  I have Magnetic Ride Control, wonder how it would play with it.  I thought I'd be doing some towing by now but haven't yet.

[dwchapmanjr]

2 hours ago, dwchapmanjr said:

GM/Chevy Protection plan just approved a new temp sensor.  Dealer read a -48F on it.  They're checking thermostat now so at the least the temp sensor is bad but approved under warranty.

High resistance in the sensor.  Replaced and it showed 175 when I took ownership again of it and stayed at 175 most of the way home (highway) although ambient is about 70F right now so its more in line.  They did not replace thermostat which based on the temp readings from the dash is fine by me.  They did a Fast Relearn on it which always helps the shifting because mine is such a low mileage vehicle it doesn't properly learn all the clutch pressures.

 

Invoice was for $2 shy of $700 but Chevy Protection plan picked up the entire bill, no deductible.

 

I noticed line item 19420015 - "A/TRANS DEXRON VI" when I drove off but when I called he assured me they use the new Mobil 1 Fluid and it is just a generic line item.

 

I'll have to drive it a couple of hundred miles to see if it resorts to its old bad habits, sometimes with my driving patterns it can take up to 6 months.

 

I also had some unrelated road vibration issues that seem to have been gone that I was troubleshooting as a suspension issue.

[Abiker21]

2 hours ago, dwchapmanjr said:

 

I also had some unrelated road vibration issues that seem to have been gone that I was troubleshooting as a suspension issue.

The positive outcome is getting most of your transmission fluid replaced. 

 

Troubleshooting the Chevy shake can drive a man insane. So many possibilities. One of my finds, was a twisted front passengers side axle. Replaced under warranty. I showed them a video of the truck on stands with the vehicle in 4wd spinning.  I was also able to spin the wheel by hand and watch the axle against the horizon and it would go up and down, but it was still tight. 

[dwchapmanjr]

2 minutes ago, Abiker21 said:

The positive outcome is getting most of your transmission fluid replaced. 

 

Troubleshooting the Chevy shake can drive a man insane. So many possibilities. One of my finds, was a twisted front passengers side axle. Replaced under warranty. I showed them a video of the truck on stands with the vehicle in 4wd spinning.  I was also able to spin the wheel by hand and watch the axle against the horizon and it would go up and down, but it was still tight. 

Agreed on the fluid, this truck has had fluid flushes/changes about every 8-10k miles of it life (due to the many revisions of PIP5337.  Hopefully that equates to the longevity of this transmission.

Yeah, I had secondarily asked them to run a picoscope on it but the service advisor was like a deer in the headlights on it.  Said he would check it out but then handed over the vehicle once the transmission issue was resolved.  He was helping out for my normal one that was on vacation so I may make a dedicated appointment for that if this transmission issue didn't mysteriously fix the shake.  I wasn't going to mix the appointments any way so I wasn't frustrated about it.

 

Mine seemed to start when my shocks were failing and after replacing them the issue didn't completely go away.  I found an obscure reference in TSB 18-NA-339 ( https://static.nhtsa.gov/odi/tsbs/2016/MC-10135275-9999.pdf ) Condition 6

Quote

The suspension will absorb larger bumps without complaints, but smaller/minor imperfections/bumps, which would normally be absorbed by the suspension, may not be absorbed as well as the owner would expect.

 

Quote

There have been some reports of Z95 MR system ride improvement following shock replacement and reprogramming the suspension control module; later to have the ride feel return to the original level of customer concern. This phenomenon occurs during a period of learning for the suspension control module of the shock characteristics. Once the learning period is complete, the module will lock in the shock characteristics for that specific vehicle.

 

[bsprtsgrp]

I'm only at 19K on my 17' Yukon Denali and have been experiencing some weird Transmission shifts and some noise while driving for the last month. I started noticing some weird rumble (like braille driving/rumbling) that I was attributing to pavement noise or tire/wheel out of balance but it’s happening now on roadway I’ve driven on prior that it has not happened on before.

 

Vehicle is going in tomorrow for the TSB 18-NA-355 Fluid Swap Out

 

https://gmauthority.com/blog/2019/08/tsb-seems-to-fix-8-speed-automatic-gm-transmission-problems/comment-page-6/

 

 

[bsprtsgrp]

Ok, mine is now swapped over to the new Mobil1 ATF, however the GM Tech told me that this is a temporary fix. He said eventually GM is going to have to replace all the Torque Converters in all these transmissions.

[dwchapmanjr]

16 minutes ago, bsprtsgrp said:

the GM Tech told me that this is a temporary fix. He said eventually GM is going to have to replace all the Torque Converters in all these transmissions.

I think it depends on how bad it was and when it was manufactured.  If you drove on it a long time with the shudder it probably did start to shred the TCC.  I'm nearly 2 years on the new fluid and its the longest its ever lasted without recurring so in my mind it is solved.  I have been through 2-3 other fluid changes.  My TCC was also replaced early on when they though tit was a manufacturing defect.  I'm about 3 years out on the new TCC.

 

During the time they thought it was a manufacturing defect there was some unsubstantiated rumor of it for 2015 and 2016.  May be true, may not be.

[bsprtsgrp]

Glazing of the TCC because of moisture in the old fluid. Heard they used Aluminum in the tranny parts to save on weight.

Edited October 21, 2020 by bsprtsgrp