HELP! Auto Trans Cooler Lines

I have a 1999 Prerunner 2.7l 3rz automatic. I had to replace the trans cooler hoses and now im confused on how to hook them back up to the radiator. Does anyone know for sure how to hook them back up to the radiator connections? I have read all over the net and most seem to say the bottom line, the one farthest back on the trans is the return and hooks up to the driver side on radiator, but my bottom hardline goes straight out and looks like it should hook to the passenger side of the radiator and the top hardline bends towards the drivers side and looks like it should hook to the driver side of the radiator. This contradicts what everyone is saying that the bottom is the return. It is possible someone replaced the hardlines and got them mixed up, that truck has 297k. Does anyone know for certain how the trans cooler lines hook up to the radiator? According to the diagram the bottom goes to the passenger side and top goes to the driver's side of radiator?

 

man i would go look for ya, but we got badass T-showers now. i think drivers side pumps INTO radiator. start the engine, put hoses in a
bucket to check.

 

I can’t imagine it matters much.

 

https://www.tacomaworld.com/threads...sions-write-up-your-4-speed-automatic.325531/

PDF files at the bottom of the first thread are what you need to check out

 

you da man @gearcruncher!

 

@gearcruncher I looked all through those pdfs. I didn't see anything about the trans cooler line routing. I'm almost certain the lower line from the trans is the return and hooks to the drivers side of the radiator. Can anyone else confirm? Is the outlet the send and inlet the return in the diagram?

 

i looked for ya. i have 03 2.7l with 340e trans. added trans cooler for towing and hauling.

from the trans followed TOP line (closest to front) to drives side in radiator.
passenger side radiator goes to cooler.
hose goes out cooler back to BOTTOM line and into trans outlet towards the back.
hope this helps.

 

@Appalachia Man Wouldn't the fluid going back into the trans be considered the inlet or return and the outlet the send or supply?

 

The return line at the rear of the transmission dumps cooled fluid back into the transmission pan .
The line at the front of the transmission is very hot as the fluid exits the torque converter on its way to the rad to be cooled .
When hot fluid reaches the radiator to be cooled it doesn't matter which way the lines are plumbed into the rad as this is a simple loop .
As long as your transmission is filled with the correct level of fluid , your transmission pump doesnt care which way you have the lines connected at the rad .

Do you have the factory repair manual for your truck ?
It will show you exactly how the lines were originally plumbed into the rad

 

my bad dude... you are correct.

 

@gearcruncher My reason for wanting to know exactly how the lines connect to the radiator is bc after i connected them back and drove for about a week i noticed my entire center console was warm and so I thought my transmission was overheating. I was thinking I mixed up the lines on the radiator. Fluid level is fine. I also did a complete fluid exchange and new filter bc the fluid was really dark and smelled horrible. Could the the new fluid change cause that excessive heat?

UPDATE I switch the lines the other day and haven't noticed my center console heating up. Top trans line (outlet, send, supply) to passenger side of radiator, bottom trans line (inlet, return) to passenger side of radiator. Same as coolant inlet and outlet flow. I'm assuming the trans fluid should be the same as coolant. Am I wrong? Someone mentioned it doesn't matter but I don't imagine you would want hot transmission fluid exiting the side with hot coolant??? That was the the way I had it hooked up originally and there was heat coming up from the center console.

 

At 297 K ,a fluid exchange with dark fluid can definitely cause an overheat issue .
Did you have the transmission pan off when you performed the fluid exchange ?
Do you have a way to scan your transmission for computer generated codes ?

 

I don't. All I have is a cheap obd2 scanner. I did drain and remove the trans pan and clean and replace screen before i did the flush. I really think I had the lines the wrong way on the radiator bc now it is fine. No more excessive heat coming up through my center console and shifter. Hope it's fine now.

 

I would think reversing the cooling lines had nothing to do with the transmission getting hot as is doesnt make sense .
It doesnt matter which way the lines go into the rad . Hot fluid entering the rad still gets cooled to engine temperature regardless of which way you connect the lines up front . If your engine overheats , so will your transmission .Your engine thermostat maintains engine and transmission temps . As the engine warms up in the morning , the warm antifreeze begins warming up the transmission .
If the transmission begins overheating and your cooling system cant keep up with the heat , your console will start getting hot
Now after a big transmission service with all new fluid and a very high detergent content , I could see the new fluid dislodging particles from inside the transmission and plugging up your torque converter solenoid . Its actually fairly common for valving to hang up after changing dirty transmission fluid . If you are travelling down the road and the locking clutch couldn't lock the transmission directly to the engine , it would create all kinds of unknown heat . Sometimes it takes a couple days for the particles to wash out of the solenoid .
This is very common and often goes un- noticed by the driver .
How much crap was in the bottom of the transmission pan ?

 

The pan wasn't that bad at all no sludge just some on the magnets, that's it.

 

@gearcruncher The heat came back. I guess you're right, it doesn't matter how the lines are hooked up to the radiator. So my torque converter solenoid might be plugged up? I'm about to go down in tire size bc my truck has such a hard time going up hills. It has 31's, and I just got some 235's, so that should help out a little. What do you suggest I do about the heat? It heats up my whole cab : (

 

Is your radiator functioning properly ?
Is the thermostat opening and closing as it should ? is your engine running hot ?
Is your clutch fan working ?
Is the transmission being cooled properly ?
Do you have transmission cooling line flow ?
I highly suggest running a scan with your cheap OBD2 scanner to see if any codes have popped up .
I am interested to see if your converter clutch is even functioning properly . 297 K is a lot of mileage .
You can add 10 aftermarket transmission coolers . If the converter is not locking , your transmission is going to get very hot .
Do you know if the transmission had regular fluid changes ? very important
Does the transmission seem to work good ? shifting 1,2,3, 4 , and converter clutch . Hows reverse ?

Sorry about the cluster of questions . The more you answer will make it easier for me to reply with a good answer

 

Personally.

I would skip the radiator cooler (cap it off) and install an aftermarket transmission cooler.

Radiator is taking hot coolant, running it down the fins. And the heat transfers through the aluminum, even though heat rises in most cases. The transfer through the aluminum makes it less efficent.

Installing aftermarket cooler will provide better cooling.

They work great if your transmisson is older, people use them for towing (uphill esp.) to help the transmisson from having to work as hard.

Buy an inline filter to run for a couple weeks, then remove it and drop/add the transmisson fluid from the pan only, and add new fluid back through the dipstick hole.

Do this 2 or 3 times total (maybe once every other oil change) until you see a nice clear red fluid.

Also make sure your gear ratio is right if youve added bigger tires or a lift. Will have alot to do with how hard other components have to work to make a full rotation. (Common Mistake)

 

For what it’s worth, I think we underestimate the efficiency of radiators. When the water leaves the bottom, it’s startlingly cool.

when I built my onboard shower, I thought I’d use the trans cooler as a way to warm the water (my truck is manual so it’s unused). Turns out that the bottom of the radiator is barely lukewarm and had no warming effect at all on my shower water, even recirculating for an hour.


So while an external cooler is probably better, especially a fan-aspirated one, the stock cooler is a lot better than you’re giving it credit for, as the longevity of our trucks support.

 

My radiator and thermostat seem to work great. No CEL. Truck reaches operating temp very quickly. Flushed the radiator the same time I did the trans, so it has brand new coolant. Trans shifts great just slow as hell like I said if im going uphill, it will downshift. I might look into installing that aftermarket cooler. Maybe that and smaller tires will help take some stress off the trans. I just bought a Bluetooth obd2 reader, so I can keep an eye on the trans temp. I'm curious to see how hot it actually is. Thanks for the advice guys.