2012 Yukon 1500 XL Denali 6.2L while driving truck shudders, rpms run up and down until engine dies. Update at #44

[testdepth]

I did look at the manual you suggested in your thread on the 6l80 but the only mention I found was on the next to last page and it was a picture only but no procedure.

Can the transmission cause the symptoms I experience with this truck? At normal engine operating temperature of 210F no issues with the truck at all. On the HWY no problems. As long as the engine is warm at 210F its fine. No DTCs or check engine light.

After cooling off for several hours or sitting over night it randomly will: Like in my video the engine stumbles and rpms rev up and down starting at about 25mph and then either will settle out or continue and then the engine stalls. But after sitting for a few minutes the truck starts back up and drives fine.

 

[testdepth]

Test drove this morning and no issues. It drove normally with AFM active. I can feel when the engine shifts from V8 to V4 every time it does it. 2 days in a row with no problem, no DTCs and no check engine.

 

[Marky Dissod]

I can feel when the engine shifts from Full@$$ to Half@$$ every time ...

Meaning that the transmission is no longer doing its job of masking the sensations of the transitions.

 

[Fless]

I did look at the manual you suggested in your thread on the 6l80 but the only mention I found was on the next to last page and it was a picture only but no procedure.

Can the transmission cause the symptoms I experience with this truck? At normal engine operating temperature of 210F no issues with the truck at all. On the HWY no problems. As long as the engine is warm at 210F its fine. No DTCs or check engine light.

After cooling off for several hours or sitting over night it randomly will: Like in my video the engine stumbles and rpms rev up and down starting at about 25mph and then either will settle out or continue and then the engine stalls. But after sitting for a few minutes the truck starts back up and drives fine.

You'll need to be sure to 'tag' @NickTransmissions in your posts if you're expecting him to see them. Otherwise it's a crap shoot.

Tag any member by entering the "@" symbol and start typing the member's name. Select from the dropdown list.

 

[testdepth]

You'll need to be sure to 'tag' @NickTransmissions in your posts if you're expecting him to see them. Otherwise it's a crap shoot.

Tag any member by entering the "@" symbol and start typing the member's name. Select from the dropdown list.

@Fless thank you for the edumacation.

 

[NickTransmissions]

I did look at the manual you suggested in your thread on the 6l80 but the only mention I found was on the next to last page and it was a picture only but no procedure.

Can the transmission cause the symptoms I experience with this truck? At normal engine operating temperature of 210F no issues with the truck at all. On the HWY no problems. As long as the engine is warm at 210F its fine. No DTCs or check engine light.

After cooling off for several hours or sitting over night it randomly will: Like in my video the engine stumbles and rpms rev up and down starting at about 25mph and then either will settle out or continue and then the engine stalls. But after sitting for a few minutes the truck starts back up and drives fine.

You need to do a full diagnosis, including engine management, ignition (including your ignition switch or equivalent), fuel delivery as well as transmission and torque converter. One symptom of failing converter/converter apply circuit in the transmission is stalling out, especially in reverse and esp when cold. This occurs due to either the clutch severely dragging against the piston inside the converter, causing the converter to pull the motor down to stalling or fluid leaking into the apply circuit due to a bad seal, o-ring, sealing ring or other leakage point, applying the clutch out of schedule.

If you have done a full diag, eliminating all of the non-transmission causes, then you only have one possibility left to explain the vehicle's behavior.

 

[testdepth]

You need to do a full diagnosis, including engine management, ignition (including your ignition switch or equivalent), fuel delivery as well as transmission and torque converter. One symptom of failing converter/converter apply circuit in the transmission is stalling out, especially in reverse and esp when cold. This occurs due to either the clutch severely dragging against the piston inside the converter, causing the converter to pull the motor down to stalling or fluid leaking into the apply circuit due to a bad seal, o-ring, sealing ring or other leakage point, applying the clutch out of schedule.

If you have done a full diag, eliminating all of the non-transmission causes, then you only have one possibility left to explain the vehicle's behavior.

@NickTransmissions Good morning Sir! Subscribed to your YOUTUBE channel by the way and please don't get rid of it. I drove this truck again this morning and nothing happened as it drove normally and now that the engine is warm it will be fine. My problem happens at low speed randomly when the engine is cold before reaching 210F. No problems in reverse or on the HWY. I just used propane and carb cleaner to check for vacuum leaks in engine bay but none were found. No vacuum leaks and fuel pressure appears normal at steady 43psi under load with this FLEX fuel engine.

I bought gauges for the transmission pressure test you suggested and getting ready to do that now if I can find the right test port on this 6L80E. Surprisingly there are no videos I can find on doing a pressure test on the installed 6L80E. Are there any other tests I can do to this transmission while installed? Drop the pan?

 

[testdepth]

I'm in southeast GA. If somehow I were to need a 6L80E transmission or rebuilt one?
I have rebuilt engines and TH350 transmissions. Is rebuilding the 6L80E something I can rebuild myself?
What rebuild kit would you recommend as there are so many out there including EBAY and AMAZON etc?
I know you are no where near Georgia so where do you recommend buying an 6L80E?

Thank you for sharing your knowledge @NickTransmissions

 

[testdepth]

I just pressure tested my 6L80E with a mechanical gauge screwed to the line pressure test port on the passenger side next to the bell housing. (7/16 bolt). Engine at normal temp of 210F. @NickTransmissions

P R N D M M2 M3 M4 M5 M6

IDLE WOT

P 84 90

R 80 230

N 85 90

D 65 170

M 65 265

M2 65 160

M3 65 150

M4 65 150

M5 65 150

M6 65 150



Are these normal numbers?

 

[NickTransmissions]

@testdepth - those numbers look good to me...At least we know your pressure regulator valve is in good shape, the pump is making pressure and the valve body's AFL valve is not worn either. Next step is to plug in the scanner to see if your TCC is coming on when it's not supposed to...If tests there are negative then your stalling is not transmission or torque converter-related.

 

[testdepth]

@NickTransmissions I was going through TSBs for my truck and found one that describes what mine is doing but it says the TSB is for 5.3 engine instead of like mine which is 6.2.

Vehicle owners may report a flare—an engine rpm increase during the shift—when the transmission shifts from 2nd to 3rd gear in cold weather.

This typically occurs when the transmission fluid is cold

• The condition is usually present only during the first few 2-3 shifts after the vehicle has been sitting for several hours.
• The flare goes away as the transmission fluid warms up.

TSB APR 2013 PI0952

Could this be my issue or have you seen this before?

 

[NickTransmissions]

@NickTransmissions I was going through TSBs for my truck and found one that describes what mine is doing but it says the TSB is for 5.3 engine instead of like mine which is 6.2.

Vehicle owners may report a flare—an engine rpm increase during the shift—when the transmission shifts from 2nd to 3rd gear in cold weather.

This typically occurs when the transmission fluid is cold

• The condition is usually present only during the first few 2-3 shifts after the vehicle has been sitting for several hours.
• The flare goes away as the transmission fluid warms up.

TSB APR 2013 PI0952

Could this be my issue or have you seen this before?

Not likely as TSBs are typically very specific when it comes to documenting impacted engine-transmission configurations. In this case, the problem is in the factory transmission control strategy/OS version loaded onto the ECM and TEHCM respectively which would be different between 5.3 and 6.2 engine applications.

 

[donjetman]

@testdepth
Here's what I did to cure my 2-3 shift flare:
https://www.tahoeyukonforum.com/thr...p0842-p0872-p0877-update.145047/#post-1838408

 

[testdepth]

@testdepth
Here's what I did to cure my 2-3 shift flare:
https://www.tahoeyukonforum.com/thr...p0842-p0872-p0877-update.145047/#post-1838408

@donjetman and @NickTransmissions

Would the pressure test show the faults donjetman shows in his video link? If I had the same problem would my pressures have been different?

 

[testdepth]

No answer ok. Thank you for everything else.