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2005 Toyota Highlander trans cooler help! #4749643
05/06/18 07:45 PM
05/06/18 07:45 PM
Joined: May 2011
Posts: 1,061
Greenville, SC via Chicago, IL
dja4260 Offline OP
dja4260  Offline OP
Joined: May 2011
Posts: 1,061
Greenville, SC via Chicago, IL
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!


2013 Hyundai Elantra Gt Hatch 6 spd
2005 Toyota Highlander V6
1997 HD Sportster
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4749660
05/06/18 07:58 PM
05/06/18 07:58 PM
Joined: May 2010
Posts: 9,621
out there
spasm3 Offline
spasm3  Offline
Joined: May 2010
Posts: 9,621
out there
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.


13 elantra 72k 5w30 QSUD
03 chevy avalanche 80k synpwr 5w30
17 mazda cx-5 7300 miles m1 0w30
Re: 2005 Toyota Highlander trans cooler help! [Re: spasm3] #4749664
05/06/18 08:00 PM
05/06/18 08:00 PM
Joined: May 2011
Posts: 1,061
Greenville, SC via Chicago, IL
dja4260 Offline OP
dja4260  Offline OP
Joined: May 2011
Posts: 1,061
Greenville, SC via Chicago, IL
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!


2013 Hyundai Elantra Gt Hatch 6 spd
2005 Toyota Highlander V6
1997 HD Sportster
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4749673
05/06/18 08:07 PM
05/06/18 08:07 PM
Joined: May 2012
Posts: 2,045
The land of USA-made Subies!
SubieRubyRoo Online happy
SubieRubyRoo  Online Happy
Joined: May 2012
Posts: 2,045
The land of USA-made Subies!
Another way is to start the truck cold with your hand on both lines. Whichever gets warm first is the line FROM the trans, so you would put the cooler on the line that stays cooler longer.

Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4749680
05/06/18 08:14 PM
05/06/18 08:14 PM
Joined: Jun 2009
Posts: 3,780
Chicago, IL
tomcat27 Offline
tomcat27  Offline
Joined: Jun 2009
Posts: 3,780
Chicago, IL
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.


2019 Cherokee, 2018 Jetta, 2014 Sentra, 1995 Escort, 1970 Cougar, 2013 XT250, 2010 Vstar, 2014 CTX1300
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4749733
05/06/18 09:00 PM
05/06/18 09:00 PM
Joined: Jun 2004
Posts: 2,684
South Carolina
bmwtechguy Offline
bmwtechguy  Offline
Joined: Jun 2004
Posts: 2,684
South Carolina
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.

Re: 2005 Toyota Highlander trans cooler help! [Re: bmwtechguy] #4749736
05/06/18 09:04 PM
05/06/18 09:04 PM
Joined: May 2010
Posts: 9,621
out there
spasm3 Offline
spasm3  Offline
Joined: May 2010
Posts: 9,621
out there
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.


13 elantra 72k 5w30 QSUD
03 chevy avalanche 80k synpwr 5w30
17 mazda cx-5 7300 miles m1 0w30
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4749809
05/06/18 11:30 PM
05/06/18 11:30 PM
Joined: Dec 2017
Posts: 417
Massachusetts
VeryNoisyPoet Offline
VeryNoisyPoet  Offline
Joined: Dec 2017
Posts: 417
Massachusetts
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.



Last edited by VeryNoisyPoet; 05/06/18 11:32 PM.

1998 V70 GLT / 195k miles [10w-30 Valvoline Syn w/ Maxlife Tech + Mann W917 filter]

"Use yah blinkah!"

"Be nice. The alternative involves an air horn and 7000 lumens of high beam."
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4750085
05/07/18 10:42 AM
05/07/18 10:42 AM
Joined: Aug 2013
Posts: 434
Alberta
tcp71 Offline
tcp71  Offline
Joined: Aug 2013
Posts: 434
Alberta
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.

Last edited by tcp71; 05/07/18 10:42 AM.

2016 F150 Eco: Edge 0w40
2005 Sienna 3.3: mobil 0w40 (varies)
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4750353
05/07/18 04:20 PM
05/07/18 04:20 PM
Joined: May 2011
Posts: 1,061
Greenville, SC via Chicago, IL
dja4260 Offline OP
dja4260  Offline OP
Joined: May 2011
Posts: 1,061
Greenville, SC via Chicago, IL
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.


2013 Hyundai Elantra Gt Hatch 6 spd
2005 Toyota Highlander V6
1997 HD Sportster
Re: 2005 Toyota Highlander trans cooler help! [Re: tcp71] #4750424
05/07/18 05:40 PM
05/07/18 05:40 PM
Joined: May 2010
Posts: 9,621
out there
spasm3 Offline
spasm3  Offline
Joined: May 2010
Posts: 9,621
out there
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.


Last edited by spasm3; 05/07/18 05:41 PM.

13 elantra 72k 5w30 QSUD
03 chevy avalanche 80k synpwr 5w30
17 mazda cx-5 7300 miles m1 0w30
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4750433
05/07/18 05:52 PM
05/07/18 05:52 PM
Joined: Dec 2017
Posts: 417
Massachusetts
VeryNoisyPoet Offline
VeryNoisyPoet  Offline
Joined: Dec 2017
Posts: 417
Massachusetts
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.


Last edited by VeryNoisyPoet; 05/07/18 05:59 PM.

1998 V70 GLT / 195k miles [10w-30 Valvoline Syn w/ Maxlife Tech + Mann W917 filter]

"Use yah blinkah!"

"Be nice. The alternative involves an air horn and 7000 lumens of high beam."
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4750437
05/07/18 05:58 PM
05/07/18 05:58 PM
Joined: Sep 2003
Posts: 1,341
Austin, TX
MaximaGuy Offline
MaximaGuy  Offline
Joined: Sep 2003
Posts: 1,341
Austin, TX
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.


2018 MB GLE350
2011 Lexus ES350
2006 Toyota Highlander 4WD
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4750502
05/07/18 06:45 PM
05/07/18 06:45 PM
Joined: May 2011
Posts: 1,061
Greenville, SC via Chicago, IL
dja4260 Offline OP
dja4260  Offline OP
Joined: May 2011
Posts: 1,061
Greenville, SC via Chicago, IL
You guys are awesome. You're making me feel lazy... blush


2013 Hyundai Elantra Gt Hatch 6 spd
2005 Toyota Highlander V6
1997 HD Sportster
Re: 2005 Toyota Highlander trans cooler help! [Re: dja4260] #4750528
05/07/18 07:04 PM
05/07/18 07:04 PM
Joined: Dec 2017
Posts: 417
Massachusetts
VeryNoisyPoet Offline
VeryNoisyPoet  Offline
Joined: Dec 2017
Posts: 417
Massachusetts
You asked, and we delivered smile

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.


1998 V70 GLT / 195k miles [10w-30 Valvoline Syn w/ Maxlife Tech + Mann W917 filter]

"Use yah blinkah!"

"Be nice. The alternative involves an air horn and 7000 lumens of high beam."
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