3rd gen Transmission Cooler Upgrade

I decided to upgrade my trucks cooling system with a larger tranmission cooler and electric fan. I haven't had any cooling problems with the OEM setup but considering I live in a desert and frequently use 4x4 and tow a travel trailer in 100+ degree temps I'll be a little happier knowing its there.


Following the rule of "use the biggest cooler that will fit" I decided on Hayden 679 tranmsission cooler which is their largest model. It also uses Haydens bypass technology which should prevent over cooling.

$52 Hayden 679 Universal 11” Rapid-Cool Add-On Transmission Cooler to Enhance Cooling (not for direct replacement of the factory unit)

https://www.amazon.com/Hayden-Automotive-679-Rapid-Cool-Transmission/dp/B000C3BBKS

I picked out a 10" Maradyne champion series fan since the flat sides fit the cooler almost perfectly and the 950 cfm rating is awesome for a fan this size.

$120 Maradyne M103K Champion Series 10" 130W Reversible S-Blade Fan

https://www.amazon.com/gp/aw/d/B005R52JKW/ref=yo_ii_img?ie=UTF8&psc=1

My plan was to run the cooler inline with the OEM air heat exchanger. I figure it would not only give some extra cooling but provide some redundancy in case I need to make a repair on the road. Haydens universal mounting brackets were perfect for installing the cooler to the core support.

I was able use the hood latch and radiator mount bolts to mount the top brackets. The bottom brackets lined up with a couple of holes in the core support so no drilling required!

It's hard to see here but the transmission fluid flows through the the radiator, into the oem cooler and onto the larger hayden cooler then back to the transmission.

*** I definatly recommend plumbing your lines when the truck is cool and transmission thermostat is closed. I only lost a couple of oz worth of fluid when disconnecting the cooler lines. Also wear some mechanics type glove when accessing the fill port. The exhaust heat shield is sharp and hot. Don't ask me why I know.... ***

Now that the oil lines are connected it's time to top off the transmission to compensate for the increased volume of the longer trans oil lines and the volume of the cooler itself.

Thanks very much too @gearcruncher for posting this thread.

https://www.tacomaworld.com/threads...be-low-on-fluid-directly-from-factory.405642/

I followed the instructions listed there and topping off fluid at home was no problem!!

I will add that temporarily pinning the transmission thermostat open as I have done here is very important since you want fluid filling the added volume while waiting for proper check temp. Just depress the thermostat with a screwdriver and insert a 1mm pin or small drill bit like I did.

Get the fluid pump made for gallon containers. The Toyota ATF WS quart containers have the larger mouth size.

A scangauge makes the process easier since it easier to tell when you're at the proper check temp. Almost there!!

I preloaded 1 quart of fluid before warming the tranmission and still had to add another half quart before fluid came out of the overflow. Either my volume maths were off or I too may have been a victim of the low ATF debacle ....

 

Well it didn't last 24 hours before I came up with some spacers and mounted the fan behind the cooler in an air puller orientaion.

Still plenty of room between the trans cooler and AC condenser/ Radiator.

Rewiring the fan was super easy and just a mater of switching the power and ground on the switch-pro terminal block to reverse the polarity. Gotta love switch-pro. There's a button for everything!


Having the fan in the puller orientaion increases the cooling efficiency while driving since the face of the cooler is now exposed to direct airflow. Another positive side effect of the fan in the pulling orientation is that there is now ALLOT more airflow coming through the fan and into the radiator. This definatly won't hurt engine coolant temps at slow speed while the fan is running!!

I also added some foam tape anywhere the longer trans lines might chaff.

A shot of the cooler through the grill.

 

RESULTS!!!
This is gonna take me a few trips to compile some data.

I can report that there has been no change in coolant temps. This is good news since there is now a rather large trans cooler blocking part of the radiator. These findings were recorded with the fan off on a spring day in Phoenix with ambient temps of 96f.

Initial scangauge trans temp readings after install are positive. TF1 readings are stable in the high 180s and and TF2 still spikes after hard driving but stabilizes very quickly to the low 190s. Before the new cooler TF1 would typically climb to TF2 readings and take longer to cool. These readings are fairly insignificant and the true test will come once I have an opportunity to tow a few times.
Those temps sound high but this trans was designed with higher operating temps than previous models. Suposedly it reduces friction and improves mpg I'm guessing the trans thermostat opens between 185 to 190f.

 

I subd them so I can organize the thread and data as I collect it lol.

 

Thanks Lord !!!
I have added your cooler write up to the AC60 series transmission page .
Hope you dont mind . We need more guys like you on this forum .
https://www.tacomaworld.com/threads/3rd-gen-transmission-cooler-upgrade.482280/#post-14723804

And for anyone reading this , take pictures whenever you do something to your truck and POST IT UP

 

Not a problem! Thanks for adding me! I plan to keep updating post #3 with trans temps I obtain while towing.
I really wish I had bought the scangauge last year so I had a better comparison. If anybody is towing with a 3rd gen and has a scangauge please post your stats i.e. trailer weight, terrain and trans temps. Thanks!!

 

Wow, this is awesome. That's a very large cooler.

When do you plan to turn the fan on?

 

I really wanted to run the extra fan for the sake of overkill. Last year during hunting season I was in 4lo pulling the trailer through mud for about a mile. That would've been an awesome time to run the fan (and have a bigger cooler). I'm sure the torque converter was spinning like crazy pulling the extra weight in 4x4 lo and mud mode engaged on the MTS system!!! I didn't have the scangauge yet but at least no dummy lights came on. I'm sure that was one of those ignorance is bliss situations
It'll also be nice to get some extra air circulating when out wheeling during the summer months.

BTW that cooler advertises 60 degree cooler temps!!! Considering this trans runs warm on the normal I might be in trouble if I ever need to work to its max potential

 

Interesting. I believe the warning comes on around 300F, so I hope it never got that hot.

I'm interested to watch your Temps when you tow

Wondering how well it will work. Why are you still running the small cooler?

 

The truck is still under warranty and my service advisor recommended leaving oem equipment in place. Basically in the event of a catastrophic failure it's very easy to return everything back to stock plumbing and drop it off at the dealer for work .
Down the road I may bypass the radiator all together and just run a huge remote cooler under the tire carrier or something similar.

 

I've doing some research in the 3rd gen Tacoma service manual. This is what I've found for normal coolant temps and thermostat operation.

Coolant thermostat opens 187-194°F
Normal coolant temperature 167 to 212°F
Max coolant temp is 284°F

Im still looking for transmission temperature information but the manual is over 11000 pages. I also emailed toyota customer service inquiring about AC60 normal operating temperatures. I wonder if I'll even get a response lol.

 

All right I was able to find some info about normal ATF operating temperatures.


Now that it's warmed up here in Phoenix I'm not too worried about over cooling. I'm gonna go pick up a 1.5mm roll pin from the hardware store and And pin the Trans thermostastat open for a couple of days of normal driving. Just curious what the temps will look like.
BTW I've read this is a Tundra trick to lower trans temps under extreme duty so maybe it'll work well on the Taco too.


*** I realized the pics are hard to read. It states normal ATF operating range is between 68F -230F. Still no info about when the trans Thermostat opens but guessing from my scangauge and normal coolant temps probably somewhere in the 190s ***

 

Sub'd

 

A quick trip to my local hardware store and I was able to find a 3/32nd (I believe) hitch pin. Works perfect for pinning the transmission thermostat open.

OK so here's how my tranmsission temps usually look. This is about the same before and after the bigger cooler.
Here's how they looked after pinning the the transmission cooler thermostat open. I did about 10 miles of hard driving on the freeway and surface streets and the pan temp never budged above 160°F yet surprisingly warmed up to that temp temp as quick as it normally warms to 190°F . The torque converter temp also stabilized much quicker to the pan temp!! It's about 86°F in phoenix today.


I'll post tomorrow if takes excessively long to warm up from cooling over night.

@gearcruncher what do you think of this? Obviously Toyota engineers wanted this trans to run between 188°F to 200°F since that where the thermostat has kept my trans temps. Running 45-50 degrees cooler would definatly extend fluid and component life and as I noted in post #13 is within normal operating temperatures.
If I don't have any issues I think I'm going to leave the thermostat pined open (especially while towing) and run cooler. Can you foresee any issues or problems?
I ask you because after reading your post I believe you're the authority on transmission info!

 

Well, thats some great research rite there !!! Excellent info !!

I dont see leaving the thermostat pinned as being an issue and this of-course is a decision based on where you live( AZ in your case ) , however , you will achieve overdrive and converter lock up earlier as the trans and engine warm if you leave the stat in the factory unpinned position and only pin the stat when needed during towing or heavy stop and go traffic . You may sacrifice a little extra fuel leaving the stat pinned during engine and transmission warm up

If one of our members from Alaska or North Dakota asked the same question , I would not recommend leaving the stat pinned .

 

Thanks for the advice! I think I'll leave it pinned through the weekend since were taking the trailer to the lake. I'll un-pin it on the way home to record the difference. After that I'll only pin it for towing and summer time trail runs.
It's literally only a matter of seconds to pin or un-pin so definatley an effective , cheap and easy mod!

 

As the worlds most boring soap opera continues more results on the pinned trans thermostat.
I started the truck up from cooling over night and let her warm up for about 1 min. It was a beautiful 70 degrees out this morning. I hoped on the freeway and had no problem finding 6th gear fm with a cruising speed of 75mph. The trans heated up to about 120°F in what I would describe as a normal amount of time. It then took quite awhile to get to the mid 140s and never broke 150°F

I ran the fan while cruising some stop and go on the regular streets. And the pan temp never broke the 130s


It'll be interesting to see the pinned vs unpinned while towing but I have a feeling it'll have no issues maintaining its normal 190s with the T-stat unpinned.

 

This is really great info - thanks for doing so much research. I too pull a travel trailer that's ~3500lbs and I'm always watching the radiator temp closely. I'm very interested in adding the scan gauge to monitor teams temps as well. I also really like the idea of pinning open the t stat when towing - that's a great idea. Hell, I might even give the extra cooling system a try - although I'm not sure the added fan is needed here in North GA. But maybe... our Summers are in he mid 90's with high humidity.

 

That trailer looks great! About the size I tow. It's a great size for a tacoma.
The bigger cooler is a relatively inexpensive upgrade for the piece of mind and potentially longer lasting parts. I've never had problems with Toyota but have seen burning hot fluid pouring through the transmission pan seal on my old Ford. I learned an expensive lesson that day and have tried to purge heat at all cost since!!
As far as pinning the transmission t stat I picked up a couple more of those hitch pins to keep in my tool bag. I figure Ill keep it pinned while towing and if I ever run into an overheating problem somewhere else that 40 cent pin just might save the day!

 

Thank you so much for all of this research!!!! I have a scan gauge II and it bothers me that I can be driving 70-75 mph and be in the 40-50s outside and my transmission is running in the 190s. I didn't know there was a thermostat on the transmission fluid. I plan on getting a camping trailer and already tow 5'x14' trailer with lawn equipment or 4 wheelers. I am going to try pinning my thermostat to see how it runs. I never allow my transmissions to run over 225° for very long. I'm always keeping an eye on my transmission fluid and used to do at least a drain and refill every 30,000 miles. Keep that info coming. I'll post my temps soon.