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1994 4L80E Cooler Circulation Loop Direction

Brewcrew

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I recently placed a 1994 4L80E into a 2002 Avalanche 2500. The cooler lines had to be shortened to accommodate the new transmission, as well as the shifter shaft etc. Now the new trans keeps running hot after an hour or so. I want to retrace my steps and make sure I have things hooked up correctly. Is the oultlet of the transmission that goes to the cooler inlet, the bottom or top fitting on the casing? I have read several forums, and someone suggested that without a doubt the circulation loop for the 1994 4L80E is the opposite of the more modern version.
 
Reverse them and see. Just cranking the engine with one line off you can see what direction the oil flow is going. IMO pumping oil in the bottom and out the top would have less air trapped in the cooler, but, the coldest coolant is in the bottom.

Do you have a trans cooler in front of the radiator? IMO it should get the oil after it goes through the radiator.

Likely you have other problems going on. I would check for codes and watch TCC slippage. Make sure the TCC is, in fact, locking up when commanded. An example: a badly running engine that misfires when the TCC locks up will have the ECM unlock the TCC to reduce load.

An unlocked TCC will generate a lot of transmission heat.

I would verify the accuracy of gauges you are using to notice it's running hot. Bad temp sensor to bad gauge in the dash ... won't be the first or last time transmissions were swapped for a false HOT reading... Make sure the trans and fluid are actually "HOT".

Not sure a 1994 is compatible with a 2002. There were many changes over the years.
 
Thanks for the reply. I replaced the aux cooler with a lager one and installed an inline booster pump. Nothing really changed. I checked the dipstick for level, and noticed in the process that the dipstick and fluid both weren’t very hot to the touch which made me think it could be a false reading. (Definitely would have thought at 250-260 it would’ve burned off my finger prints lol). Anyhow, the fluid was bright red, did not smell etc., so I thought it could be a difference in resistance from the wiring of the older transmission to the newer from the temperature transmitter to the gauge giving me a false reading. I’m going to go through some steps to troubleshoot this weekend to see if the temp is real, including an infrared heat gun to check pan temp, and TC temp relative to the gauge reading. I will unhook one of the lines to find the flow direction also. Thanks again, I’ll let ya’ll know what I find.
 
I’m not sure I can answer that intelligently. I guess I would have to use the “look and see” approach on that one. I hadn’t thought of that. Thanks
 
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