Overheating transmission

[StephenW]

2015 -Yukon XL Denali with 190k miles. Transmission overheated 2 days ago. Changed out the fluid and filter (overdue). Nothing remarkable on the magnet or in the fluid - just dirty.

Just drove it after the change out and temp was 225-250 and rising in 25 min of driving. Am I just screwed into a transmission replacement?

 

[MobileHomie]

Do you know what caused it to overheat the first time?

 

[StephenW]

No. Assumed dirty fluid/clogged filter.

 

[tom3]

Does this year have the thermal control valve on the side of the transmission where the cooling lines connect? That could be stuck or plugged somehow.

 

[StephenW]

Yeah unfortunately I am not savy on the system. I would love a diagram to see how everything flows and what could be a fail point. Like - is there a TXV or thermostat that could have failed?

 

[NickTransmissions]

Install a Superior Tech delete kit or flip the pill. Either will help keep trans temps in check.

That stupid ass cbv likes to fail, overheating the trans and burns up the 4-5-6 clutch pack.

 

[StephenW]

Cbv?

 

[NickTransmissions]

Cbv?

Cooler Bypass Valve aka Thermal Bypass Valve aka Transmission thermostat.

Check out the Tech Svc Bulletion if you havent see it already. There's an updated CBV from GM but it simply lowers the temp the thermostat begins to open. Id rather delete it all together...

 

[StephenW]

This the superior product you referring to?

Superior STL010 | Superior Transmission Parts - The problem solvers of the transmission industry

 

[NickTransmissions]

Yep

 

[MobileHomie]

@NickTransmissions,
Thank you for posting the product that bypasses the t-stat transmission killer!
Is there a deeper aftermarket pan that has a dipstick?

 

[NickTransmissions]

@NickTransmissions,
Thank you for posting the product that bypasses the t-stat transmission killer!
Is there a deeper aftermarket pan that has a dipstick?

I think so - check Summit Racing or Jegs to see what's available.

 

[CMoore711]

Do you have the 8 speed or the 6 speed transmission?
190K miles just changed fluid a few days ago… How often was the transmission fluid changed for that first 190K miles?

 

[StephenW]

Pretty sure 6 speed. Not very frequently.

 

[Marky Dissod]

2015 -Yukon XL Denali with 190k miles. Transmission overheated 2 days ago.
Changed out the fluid and filter (overdue). Nothing remarkable on the magnet or in the fluid - just dirty.
Just drove it after the change out and temp was 225F-250F and rising in 25 min of driving.
Am I just screwed into a transmission replacement?

Pretty sure 6 speed. Not very frequently.

More like aged into a transmission replacement.
Regular Production Order 'MYC' = 6L80E
If your Service Parts Identification sticker lacks that particular three-letter code, you've an 8L90E (8L90E RPO code escapes me).

 

[arkie]

More like aged into a transmission replacement.
Regular Production Order 'MYC' = 6L80E
If your Service Parts Identification sticker lacks that particular three-letter code, you've an 8L90E (8L90E RPO code escapes me).

M5U or M5X should be the 8L90