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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: chevn-up on April 03, 2023, 05:02:55 PM
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Maybe this question has been asked before. I have a 85 th350c. 1/2 ton 2wd 305 engine. ac also. My question is does the fluid flow from the trans to the top fitting of my radiator, and then back to the trans, or the bottom fitting first, then back ? All this because I want to add an external cooler.
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See image
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Super. Thanx.
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This is always a topic of conversation. I feel it somewhat depends on where you are located geographically and how you use your truck.
The bottom port on the TH350 is the Outlet from the transmission (HOT), and the top port is the inlet from the cooler (COOL).
I have always plumbed my auxiliary cooler first and then come back into the top of the radiator and then back out to the transmission from the bottom of the radiator. In this way, the transmission fluid doesn't get too cold when running in colder weather. If transmission fluid is too cold, it gets thick and shifting will be impacted. I will admit I have never run tests plumbing them this way or the way Vile has shown. I drive my trucks in all weather conditions and have never had a problem with plumbing them this way. I also have my '69 Chevelle plumbed that way and have never had a problem in the heat of summer.
The stock lines will usually have the bottom (HOT) port of the transmission going to the top of the radiator and the bottom of the radiator going to the top (COOL/Inlet) port of the transmission.
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All good info! Knowing the trans top/bottom ports is half the work. The radiator is not bias as to which direction fluid is pumped, so trace the lines two or three times to be sure. And THEN, graft-in the aux. cooler. Cool.