2005 Toyota Highlander trans cooler help!

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Going to start towing a small boat/trailer this summer.


I'd like to add a trans cooler. I can't find any diagrams that would show the input line and exit line back to the trans. I'm also not sure what aftermarket unit would be sufficient. Fully loaded the boat/trailer won't be over ~1600 lbs. I don't want to purchase the OEM cooler as it's almost $200 dollars. I have many options in the $30-50 range.

Any insight would be awesome!
 
I would unhook the top trans line to the radiator. Have someone start it up for a moment and see whether fluid pours from the line or the radiator.

If it pours from the radiator, the top line is the return. If if pours from the line that's disconnected, then the bottom line is the return.
 
Originally Posted By: spasm3
I would unhook the top trans line to the radiator. Have someone start it up for a moment and see whether fluid pours from the line or the radiator.

If it pours from the radiator, the top line is the return. If if pours from the line that's disconnected, then the bottom line is the return.


It's that easy?!?!?

I'm struggling to find a trans diagram that shows the lines. That's a great start!
 
Or use an infra red thermometer to check the temp on the lines. Pick a cooler with around 50 to 70 square inches of surface.
 
Not sure about your Highlander, but some newer cars are using a mini heat exchanger mounted directly on the transmission so all you might see is coolant hoses going to the transmission cooler and back to the engine or radiator. You will know if yours has this setup if you cannot find any transmission cooler lines or hoses. Without a special adapter, it is nearly impossible to add an aux cooler to these vehicles. My father in law retired from rebuilding transmissions, but designs, manufactures and sells adapters for several models to allow the easy/inexpensive replacement of too-small factory coolers with a larger, more effective coolers that connect with standard trans cooler hoses to his adapters.
 
Originally Posted By: bmwtechguy
Not sure about your Highlander, but some newer cars are using a mini heat exchanger mounted directly on the transmission so all you might see is coolant hoses going to the transmission cooler and back to the engine or radiator. You will know if yours has this setup if you cannot find any transmission cooler lines or hoses. Without a special adapter, it is nearly impossible to add an aux cooler to these vehicles. My father in law retired from rebuilding transmissions, but designs, manufactures and sells adapters for several models to allow the easy/inexpensive replacement of too-small factory coolers with a larger, more effective coolers that connect with standard trans cooler hoses to his adapters.


I think my mazda cx-5 has this, no transfluid running to the radiator.
 
Not 100% sure this diagram is accurate, but this shows part 32922 is the outlet and 32921 as the inlet. Interesting how they seem to run fluid through the OEM external cooler before running it through the radiator end tank cooler if I'm reading this right.

https://parts.toyota.com/a/Toyota_2005_H...22410-3514.html

I haven't really put it through the paces yet, but I just installed a Hayden 676 Rapid-Cool (6" x 11") compact plate and fin cooler, which made a big difference as seen on my ATF temp gauge. Maybe the 677 (7.5" x 11") would be a better fit for your case since you plan on towing.

If you go for a custom external cooler, I would pipe it so hot ATF flows through the radiator first and sheds some heat, then flows through the external cooler, then returns to the transmission. Consider adding an oil thermostat between the radiator cooler and the external cooler. This will let the transmission warm up quickly for best efficiency, then allow maximum cooling once it gets hot. You can then put on a pretty large external cooler but not have to worry about the fluid being too cold in the winter.

In addition to adding the cooler, watch the tach and feel if the transmission hunts between gears or can't keep the torque converter locked up, especially if you have to climb a grade. This will show up as the RPM bogging down, a downshift and the engine roaring in the lower gear, then an upshift where the cycle repeats. Drop it out of drive into the next lowest selection to let the converter lock again and stop the gear hunting. Even with an extra cooler you can still roast the transmission if the converter doesn't lock up and it keeps hunting between gears.
 
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I had one on our 2005 Sienna with the same engine. It had the "in radiator" cooler as part of the tow package, but no external cooler. I put a hayden 1678 in the loop after the radiator when we were towing our trailer with the van. You can monitor the transmission temps on the U151e/f transmission with an OBDII reader. I used a scangauge II and the highest temp I ever saw was 221f. It worked very well.
 
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I looked under the hood and couldn't really find coolant lines visible from the trans to the radiator. The provided diagram isn't accurate as I don't have the trailer package with the OEM trans cooler. My vehicle is the 3.3 v6, 2wd.
 
Originally Posted By: tcp71
I used a scangauge II and the highest temp I ever saw was 221f. It worked very well.


That's hotter than i would want.

transmission-temperature-chart.jpg
 
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Originally Posted By: dja4260
I don't have the trailer package with the OEM trans cooler. My vehicle is the 3.3 v6, 2wd.


I searched up for the 2wd 3.3 V6 and got the exact same diagram. The optional OEM cooler is shown in the diagram just so they don't need to make a separate diagram for it.

Here's a video talking about radiator replacement on a 2005 3.3 V6. Starting at 0:36 it shows the fittings where the transmission cooler lines attach to the bottom of the radiator. At 2:03 it shows the bottom splash guard / air tray that needs to come off to access the bottom of the radiator.




EDIT: Here's a more in depth video showing full radiator replacement on a 2004 2.4L I4, that shows how to remove the front tray at 0:30. It shows removing the transmission cooler lines at 2:37.
 
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Have a V6 highlander with a towing package. Looking down at the radiator, the cooler line from the bottom of the radiator (right side next to the radiator drain plastic bolt) goes into the cooler and the out from the cooler goes into the transmissions right sideline.
 
You asked, and we delivered
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From the looks of things, you should be able to add the external cooler pretty easily. Would also be wise to replace the existing OEM cooler hoses while you're under there if they are original, as they may be starting to weep by now (or will start after you disturb them). You can either buy OEM, or use bulk hot oil rated hose which will save you a fair bit of money.

Most cooler kits will come with a few feet of hose, and you can buy additional hose separately.
 
There is plenty of space below the battery to install a decent size cooler, infact the cooler which comes in the towing package is towards the right of the battery at the same level as the radiator bottom. So there is plenty of space below the battery for a good install
 
Just make sure there is airflow over the cooler. Ideally you want it where your clutchfan/electic fan can pull air across it. Important if your are in bumper to bumper traffic barely moving.
 
Originally Posted By: spasm3
Just make sure there is airflow over the cooler. Ideally you want it where your clutchfan/electic fan can pull air across it. Important if your are in bumper to bumper traffic barely moving.


or get a cooler with a fan on it?
 
Originally Posted By: MaximaGuy
Have a V6 highlander with a towing package. Looking down at the radiator, the cooler line from the bottom of the radiator (right side next to the radiator drain plastic bolt) goes into the cooler and the out from the cooler goes into the transmissions right sideline.



+1 I have a 2005 Highlander 3.3L V6 AWD with towing package. Routing is as described above.

Just a thought. You might consider pulling the cooler assembly, brackets, lines etc. from a junked car. It might be a lot easier to install.

Sam
 
Originally Posted By: Sam_Julier
Just a thought. You might consider pulling the cooler assembly, brackets, lines etc. from a junked car. It might be a lot easier to install.


This would work, but flush a used cooler and lines very well before installing. Would ruin your day and wallet if there is debris from a dying transmission trapped in there that gets pushed through and chews up your working transmission once installed.
 
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