Lower Transmission temp. Updated GM TBV vs STL010 6L80 8L90 10L90

[2018GMC]

Anyone install the STL010 or updated GM transmission thermostat?

 

I don’t want to do the pill flip because I live in an area where we get below freezing temps and 4 full seasons. 
 

Not sure if my 2018 8L90 has the updated part. It’s hard to read what number is stamped in the trans thermostat. 
 

my trans temps are always 180 - 200 during the summer and maybe got to 205 when crossing the desert with outside temps 115 - 118

 

https://static.nhtsa.gov/odi/tsbs/2021/MC-10207911-9999.pdf

Edited October 22, 2023 by 2018GMC

[Grumpy Bear]

First this TBS is for the 6 speed 6L80E or 6L90E. The STL010 kit works because the TBV internals are all identical between the 6, 8 and 10 speed models, meaning one could buy the TBV for the six speed and swap pills. The pill cannot be bought separately. 

 

Second, the STL010 does the same thing a pill flip with the ability to short circuit cooler if it should plug. It will not plug from cold fluid.  

 

Third, prior to 2014 the six speeds didn't use a TBV nor have most automatics from any manufacture since the early 1960's and many yet today like the 6T45E. Nor did any provide and internal bypass for cold weather. The STL010 is a solution in search of a problem.

 

Fourth, in factory form the ATF in the winter, especially in vehicles used in trips under 25 miles will experience the same ATF temperatures no matter what method you use. From 25 miles and onward the 70C pill will hold a higher temperature than any other method or device.

 

   

 

 

[2018GMC]

@Grumpy Bear Thanks for the detailed explanation. 

[newdude]

8 speeds seem to not mind the heat.  What they do mind is the wrong fluid or the original, outdated fluid that causes the notorious "8 speed shudder".  

 

Being you are in Arizona and exposed to high heat, best option is a shortened drain interval aka the severe use schedule in the owners manual.  Change the ATF (Mobil 1 LV ATF Synthetic HP ONLY) every 45,000mi.  The temps you see now are what I see in NY with my 8 speed, even on a hot 90 degree day.  

[2018GMC]

2 hours ago, newdude said:

8 speeds seem to not mind the heat.  What they do mind is the wrong fluid or the original, outdated fluid that causes the notorious "8 speed shudder".  

 

Being you are in Arizona and exposed to high heat, best option is a shortened drain interval aka the severe use schedule in the owners manual.  Change the ATF (Mobil 1 LV ATF Synthetic HP ONLY) every 45,000mi.  The temps you see now are what I see in NY with my 8 speed, even on a hot 90 degree day.  

I hear ya. I changed the fluid myself, did the driveway flush and exchanged 12qts with the new blue label fluid. My 2018 only has 23K on it but I wanted to change out the factory fluid that can absorb moisture. 
 

I still get the odd clunky mixup shift every once in awhile in stop and go traffic but I’ve never had the shudder issue and don’t want to experience it.