Thermal Bypass Valve Inlet and Outlet

[Gangly]

Does anybody know which of the two tubes on the Thermal Bypass Valve of an 8l90 is going to the cooler and which is coming from the cooler?  

[Grumpy Bear]

See the end plug and snap ring?

Line closest to that is going to the cooler. (top in photo)

The one further away is the return from the cooler. (bottom in photo)

 

Edited February 24, 2023 by Grumpy Bear

[Gangly]

Thanks Grumpy. 

I found a leak at the transfercase/transmission extension housing so I decided to go ahead and change the transfer case and transmission fluids.  I figured heck, since I'm changing fluids, I might as well upgrade the TBV with the Superior Solutions STL010 so I don't have to go through the whole heat up and cool down process to change fluids and check levels.  Then I got to thinking "hey, since I'm pulling these lines, I might as well do a "garage flush" for the transmission and I figured I would use one of the two ports on the TBV to do so.  If I cant flush from there, I'll disconnect from the cooler at the front of the truck and flush from there.  Now that I think about it, flushing from the cooler at the front is the much more logical location.

 

I'm just waiting on a few gaskets and seals to come in.  Amazingly, the gasket for the TBV is on a 1-2 week backorder, and the transmission output shaft seal is a couple weeks as well.

 

I'm rambling, I know.  Thanks again for the insight on the tubes, I appreciate it.

Edited February 24, 2023 by Gangly

[Grumpy Bear]

That gasket is reusable. I've reused mine about 4 times trying different things. 

[Gangly]

2 hours ago, Grumpy Bear said:

That gasket is reusable. I've reused mine about 4 times trying different things. 

Thanks for the heads up, I can knock out the TBV install while I wait for the other parts.