6L80 Thermal Bypass Doesn't match videos for 'pill flip' or Shift Technology modification

[Brian Maxwell]

I purchased the Shift Technology thermal bypass modification kit and went to install it today but the existing bypass housing and internals don't match anything I can find.

When I dissassembled it, there was a pin in the center and a cylindrical piece that sits on top of the pin and resides up in the end cap permanently.

There is no passage between the two sides (plug both top holes and blow in it and air goes nowhere).

 

Is this already some sort of aftermarket bypass which would be permanently open?

- If so, why bother with the pin and cylendrical bit?

 

The transmission runs quite a bit warmer than I'd expect if it were fully bypassed.  I got this because I've already had the trans rebuilt once and a billet converter installed and I don't want to do it again.

 

What would you do?

[rav3]

Are you the original owner? If not, PO could have modified it. Just a guess.

[mikeyk101]

I still have my original and opened it up. Yours is definitely different than a stock one. I already see yours is missing the "pill" and the spring. That pin goes inside the skinny part of the pill and protrudes from there. Here are the parts that are normally inside.

 

And here is a view inside the actual housing.

 

 

You can see the hole at bottom is much bigger. Also, with the guts removed, air is flowing freely through either tube on mine.

[Brian Maxwell]

1 hour ago, rav3 said:

Are you the original owner? If not, PO could have modified it. Just a guess.

Nope.  That's what I figured.

[Brian Maxwell]

So I'm correct that with no passage between, it's essentially always allowing coolant to flow through the lines right?

[rav3]

Not sure about your statement "with no passage between".....I can't remember exactly how, but with the "pill" flipped, it allowed ATF to flow continually to the cooler. That's how these trucks used to work before the K2XX generation truck came along. Best way to know if it was allowing ATF to flow through was by the temperature of your ATF fluid on the dash display. If it stayed below the 150 F temp, for the post part, the bypass was working however the PO modified it. Hope that makes sense 

[rlcole321]

The reason for the Trans Tstat is because the trans fluid does not go thru the radiator like old school, it goes thur the top part of the AC condenser, so since there's no warm coolant to "warm up" the trans, the tstat does it. They do have an updated 152 degree trans thermal valve, you should get that. Just like your engine, you want your trans to be warmed up a little too.

[mikeyk101]

7 minutes ago, rav3 said:

Not sure about your statement "with no passage between".....I can't remember exactly how, but with the "pill" flipped, it allowed ATF to flow continually to the cooler. That's how these trucks used to work before the K2XX generation truck came along. Best way to know if it was allowing ATF to flow through was by the temperature of your ATF fluid on the dash display. If it stayed below the 150 F temp, for the post part, the bypass was working however the PO modified it. Hope that makes sense 

 

In stock configuration, the spring is all the way inside hole at bottom first and the "pill" has fat end down towards the bottom and pin is inside the skinny part of "pill". For the mod, the pill goes in first with skinny part towards the bottom and the spring goes on top of the pill before putting top part back on.

[mikeyk101]

...nevermind...

Edited March 8, 2025 by mikeyk101

[rav3]

Don't over think it. Just install your new bypass kit & move on.

Everyone has an opinion on what's best or not. GM was forced to install the bypass due to EPA regulations to make the fluid run thinner for less drag since the fluid would be hotter. But heat kills ATF which in turn kills torque converter, which kills transmissions. They came out with a cheap work around with the cooler temp bypass but they still run too hot (IMO). My older 4L60 never had a bypass & transmission worked fine & they lasted longer that today's transmissions.

Search YouTube for videos on this & transmission rebuilds will tell you HEAT KILLS ATF & to get rid of the bypass. Good luck with it & be glad the PO did his deleat.

[Brian Maxwell]

4 hours ago, rav3 said:

Don't over think it. Just install your new bypass kit & move on.

Everyone has an opinion on what's best or not. GM was forced to install the bypass due to EPA regulations to make the fluid run thinner for less drag since the fluid would be hotter. But heat kills ATF which in turn kills torque converter, which kills transmissions. They came out with a cheap work around with the cooler temp bypass but they still run too hot (IMO). My older 4L60 never had a bypass & transmission worked fine & they lasted longer that today's transmissions.

Search YouTube for videos on this & transmission rebuilds will tell you HEAT KILLS ATF & to get rid of the bypass. Good luck with it & be glad the PO did his deleat.

Yeah.  Asking because the kit won't work with this housing.  I'll probably order a full aftermarket housing or the updated GM one.

[Brian Maxwell]

5 hours ago, mikeyk101 said:

 

In stock configuration, the spring is all the way inside hole at bottom first and the "pill" has fat end down towards the bottom and pin is inside the skinny part of "pill". For the mod, the pill goes in first with skinny part towards the bottom and the spring goes on top of the pill before putting top part back on.

So the pill is then sealing the internal passage.  It would stand to reason then that what I've got is a permanent block since there's no passage.

[mikeyk101]

53 minutes ago, Brian Maxwell said:

Yeah.  Asking because the kit won't work with this housing.  I'll probably order a full aftermarket housing or the updated GM one.

 

I think you're on the right track. These are easy enough to get to and swap out. The updated OEM one probably makes the most sense. And then you will still have the option of doing the pill flip later if you wish. I installed the updated one a few years back and then had a trans failure last spring that required a reman one installed. The thermal bypass valve from original trans got swapped over to the reman one. It seemed to run just a tad warmer than it did with the original trans so I did the pill flip. Temps are much more reasonable now.

[newdude]

The late 2016 to old body 2019 6 speeds run too cool (IMO) when bypassed/SureCool'd.  If you have winters and cold where you are, it will MAYBE get to 100F in the winter which isn't great for drivability reasons (shifts better with temps closer to 130-160F).    

 

The move to make on a 2016.5-2019 is the updated GM TBV with the 158F thermostat.  I ended up using that one on my 2019 old body after driving a week with it bypassed in the winter.  With the lower temp TBV it never got hotter than 167F on a hot summer day making back to back WOT pulls with it.  

[newdude]

6 hours ago, rlcole321 said:

The reason for the Trans Tstat is because the trans fluid does not go thru the radiator like old school, it goes thur the top part of the AC condenser, so since there's no warm coolant to "warm up" the trans, the tstat does it. They do have an updated 152 degree trans thermal valve, you should get that. Just like your engine, you want your trans to be warmed up a little too.

 

 

Depends on the model year and engine. 

 

V6s don't have the aux cooler in the condenser and just go to the radiator side tank ATF cooler.

 

2014-early 2016 V8 1500s the lines go through the radiator FIRST and then out to the condenser combi-cooler.  These ones run warmer with both the lower temp TBV or a bypass/surecool.

 

2016.5-2019 "LD" 1500s with V8, those do NOT go through the radiator at all.  Its transmission straight to the condenser combi-cooler.  These run too cold when bypassed/surecool in the winter but run 115-130F in the summer, but are really dialed in with the lower temp TBV and run 120-140F winter, 145-170F summer.