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GM Transmissions

dna9656

By dna9656
in Engines & Drivetrain

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newdude Senior Enthusiast

newdude

Posted
Posted
2 hours ago, dna9656 said:

You appear to be a fountain of information; thank you for exposing the secret(s) of OD 2 to the rest of us. Most of US are just people trying to make sense of some part of our world we all live in. Thank you for your revelations on modern OBD 2 operations.

 

 

 

Secrets?  Revelations?  Its nothing new.  OBD2 has been around since 1996.  The networking it what's changed the most in the vehicle electrical platforms.  Programming has been a thing for a long time, its just now almost every single module in these cars needs programming or can be re-programmed to fix issues.  

  • Like 1
asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted
18 hours ago, newdude said:

Depends.  If contaminates get into the TEHCM solenoids, the it needs a new one.  

 

Its technical name is the Transmission Electro-Hydraulic Control Module or TEHCM.  

 

There are multiple reasons the TEHCM needs programming or the shift adapts learned.  Transmission shift adapts need to be learned for the following reasons on the 6L80/6L90:

 

Transmission internal service/overhaul

Valve body repair or replacement

Control solenoid valve assembly replacement

TCM software/calibration update

Any service in response to a shift quality concern

 

If the TEHCM is replaced, not only does it need the shift adapts but before that it needs to be programmed to the vehicle all together as new ones arrive blank aside from any default testing programming.  

Can those solenoids be flushed?

 

I also wonder how bad would it be if you chose not to reset the the shift adapts... it would eventually adapt to the new hardware. Seems like I recall a battery disconnect resets them too (but that is a fleeting memory).

 

I also wonder about salvaged TEHCM - if it is programmed to a comparable truck why wouldn't it work - are they VIN locked?

 

In the end I think the thought about how big a deal programming these things are is being over-stated. It adds what to the rebuild cost? 300.00? But if one is really trying to avoid this...

newdude Senior Enthusiast

newdude

Posted
Posted
28 minutes ago, asilverblazer said:

Can those solenoids be flushed?

 

I also wonder how bad would it be if you chose not to reset the the shift adapts... it would eventually adapt to the new hardware. Seems like I recall a battery disconnect resets them too (but that is a fleeting memory).

 

I also wonder about salvaged TEHCM - if it is programmed to a comparable truck why wouldn't it work - are they VIN locked?

 

In the end I think the thought about how big a deal programming these things are is being over-stated. It adds what to the rebuild cost? 300.00? But if one is really trying to avoid this...

 

 

The only thing I see would be a piston and seal kit from Sonnax.  How to Rebuild GM 6L & 6T TEHCM Pressure Switches| Sonnax

 

Other than that, I don't think there is a way to clean the internals out.  

 

Used transmissions (or TEHCMs for that matter) can be re-flashed and re-adapted to a new vehicle.  

 

Programming isn't a big deal really.  Is it an inconvenience?  Sure, especially to those who grew up wrenching on old stuff where programming was never a thing.  But now, all the GM 6, 8, 9 and 10 speeds, no matter where the TCM is mounted (external to the transmission or internal) require either programming, reprogramming or shift adapt when replacing with new, replacing with used or rebuilding/overhauling an existing transmission.  Its just a part of it and has been for at least 17-18 years.  

  • Like 2
  • 2 weeks later...
TriZZZl3 Enthusiast

TriZZZl3

Posted
Posted

Looking for some input. 
 

I drive a 2016 Sierra 5.3 with 8L90 and purchased a 2018 8L90 from a 6.2. It’s installed, accepted characterization and relearn performed. Truck cranks but will not engage to gear. I’ve recently learned that the TCMs changed in 2017-2018 to the T87a. If I purchase the new TCM and have it programmed to my VIN, recharacterized and relearned, will this solve it?  
 

I’m worried about communication with ECM. I can’t find any information on this topic. 

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