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6L80 Trans pill flip maintenance question

mikeyk101

By mikeyk101
in Modifications & Accessories

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mikeyk101 Senior Enthusiast

mikeyk101

Posted
Posted (edited)

So I'm a bit confused on this still and tried searching but no luck. I did the pill flip on my 6L80 trans thermostat because it made a lot of sense.  The trans does run cooler now than it did. But I have an ESP that covers pretty much everything until 2025 or 125,000 miles. I'm only just over half the mileage now so many more miles on the coverage.

 

So my understanding is that when having the transmission fluid changed, part of the procedure is to get the trans temp up to "operating" temperature which I assume is in the neighborhood of 190⁰. Before the mod, it didn't take very long for this to happen. But by doing the pill flip, this could be an issue as it will be a lot more difficult to get the trans to warm up to the "operating" temperature. Pretty much all of my service is done at the dealerships so that a record of performed service is maintained. So my conundrum is when I have fluid flushed again, do I inform the dealership that I did the thermostat delete (pill flip) and potentially cause issues with my ESP coverage or just keep my trap shut and the dealership will never know and still be able to service the transmission as before? I guess I could always switch it back and wouldn't take very long to do but would rather not have to do that...

 

Just to add, I had the Trans fluid exchange done in Oct 2020 and the service supposedly used 12 quarts of Dexron VI for the service. So this won't be anything I will probably need for a while.

Edited by mikeyk101
newdude Senior Enthusiast

newdude

Posted
Posted (edited)

Hot check is done between 160-200F.  So in a 2007-2019 HD gas truck which never had a thermostat, you'd just need to get it to 160F at a minimum for a proper hot level check.  That would be how you'd hot check a thermostat bypass truck.  

 

If they flush it again, they'd be able to do a cold check (80-90F) or at least check it while the temp is say 100-130F sitting in the shop, and then just check it yourself when you've got a day where you can get the temps up.  

 

Your OTHER option is to install the NEW thermostat GM offers.  The new one is full open at 158F.  Here is a link on the document for it:

 

Thermal Bypass Valve Installation – TechLink (gm-techlink.com)

 

The valve p/n is 86774933.  You also need the gasket p/n 23135703.

 

Edited by newdude
  • Like 2
  • Thanks 2
UnlimitedMatt Enthusiast

UnlimitedMatt

Posted
Posted
57 minutes ago, newdude said:

Hot check is done between 160-200F.  So in a 2007-2019 HD gas truck which never had a thermostat, you'd just need to get it to 160F at a minimum for a proper hot level check.  That would be how you'd hot check a thermostat bypass truck.  

 

If they flush it again, they'd be able to do a cold check (80-90F) or at least check it while the temp is say 100-130F sitting in the shop, and then just check it yourself when you've got a day where you can get the temps up.  

 

Your OTHER option is to install the NEW thermostat GM offers.  The new one is full open at 158F.  Here is a link on the document for it:

 

Thermal Bypass Valve Installation – TechLink (gm-techlink.com)

 

The valve p/n is 86774933.  You also need the gasket p/n 23135703.

 

This is good news!  I can't wait to hear how this new thermostat works for folks here.  

  • Like 1
mikeyk101 Senior Enthusiast

mikeyk101

Posted
  • Author
Posted
2 hours ago, Grumpy Bear said:

Are you saying the did the fluid flush AFTER you did the pill flip?

No, I did pill flip after the trans fluid exchange. I just want to be ready for the next time I have it done.

dieselfan1 Senior Enthusiast

dieselfan1

Posted
Posted
6 minutes ago, mikeyk101 said:

No, I did pill flip after the trans fluid exchange. I just want to be ready for the next time I have it done.

I did the same.

I'll just flip it back next flush then re flip it. It's easy.

  • Like 3
mikeyk101 Senior Enthusiast

mikeyk101

Posted
  • Author
Posted
1 hour ago, newdude said:

Hot check is done between 160-200F.  So in a 2007-2019 HD gas truck which never had a thermostat, you'd just need to get it to 160F at a minimum for a proper hot level check.  That would be how you'd hot check a thermostat bypass truck.  

 

If they flush it again, they'd be able to do a cold check (80-90F) or at least check it while the temp is say 100-130F sitting in the shop, and then just check it yourself when you've got a day where you can get the temps up.  

 

Your OTHER option is to install the NEW thermostat GM offers.  The new one is full open at 158F.  Here is a link on the document for it:

 

Thermal Bypass Valve Installation – TechLink (gm-techlink.com)

 

The valve p/n is 86774933.  You also need the gasket p/n 23135703.

 

Excellent info! I tried a search of that bulletin and came up a blank. But then did a search of that new thermostat part number and mist of the document is posted in this thread:

https://www.silveradosierra.com/threads/new-gm-tsb-for-thermal-bypass-valve.742585/

 

I found the new thermostat online and it can be had for around $50. But reading what was posted of that document, it is going to be a swap out by the dealer depending on complaints. I wish the first page had been posted...

  • Like 1
mikeyk101 Senior Enthusiast

mikeyk101

Posted
  • Author
Posted

And it looks like it would be a great alternative. Active cooling at 154⁰F sure beats 190⁰ and would be a genuine GM part instead of doing the diy pill flip and that would negate any arguments. Like many others, I think that the 190⁰ trigger was way too high to begin with and it seems that GM would agree...

  • Like 2
Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
3 hours ago, newdude said:

Hot check is done between 160-200F.  So in a 2007-2019 HD gas truck which never had a thermostat, you'd just need to get it to 160F at a minimum for a proper hot level check.  That would be how you'd hot check a thermostat bypass truck.  

 

If they flush it again, they'd be able to do a cold check (80-90F) or at least check it while the temp is say 100-130F sitting in the shop, and then just check it yourself when you've got a day where you can get the temps up.  

 

Your OTHER option is to install the NEW thermostat GM offers.  The new one is full open at 158F.  Here is a link on the document for it:

 

Thermal Bypass Valve Installation – TechLink (gm-techlink.com)

 

The valve p/n is 86774933.  You also need the gasket p/n 23135703.

 

 

That sir is serious good news. THANKS!!

  • Like 1
newdude Senior Enthusiast

newdude

Posted
Posted
14 hours ago, mikeyk101 said:

Excellent info! I tried a search of that bulletin and came up a blank. But then did a search of that new thermostat part number and mist of the document is posted in this thread:

https://www.silveradosierra.com/threads/new-gm-tsb-for-thermal-bypass-valve.742585/

 

I found the new thermostat online and it can be had for around $50. But reading what was posted of that document, it is going to be a swap out by the dealer depending on complaints. I wish the first page had been posted...

 

 

The new one can be swapped in at any time.  If its under warranty and is in for transmission issues, GM says to install it no matter what.  That's what the "depending on complaints" part is about, if its under warranty.  That's why it has those labor ops on the last page for warranty use.  

 

  • Like 4
Salsa De Piña Enthusiast

Salsa De Piña

Posted
Posted

So if I'm reading this correctly, I can show up complaining about harsh shifts under warranty (which they won't be able to duplicate because the truck is shifting just fine) and they'll swap in the new thermostat?

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