TRANSMISSION . Transmission coolers for all Toyotas ... Write up with many pictures

Congrats.

 

Is a bypass cooler absolutely necessary in cold climates? I live in MN, we will see -20f temps often enough.

I ordered a

$58 Hayden 679 Universal 11” Rapid-Cool Add-On Transmission Cooler to Enhance Cooling (not for direct replacement of the factory unit)

Hayden 679 and have it mounted but no lines run to it yet, but now after reading more I'm second guessing for a 698 or 699 with bypass.

My understanding is the 3rd gen with tow package has a warmer system at the tstat that utilizes coolant to warm the trans oil (all pre-cooler system). The tstat doesn't open and circulate oil through the coolers until ~187deg, so my original thought was a bypass at the cooler wasn't needed since it should already be at least 187deg, and in my head this still makes sense, but seeing everyone with reports of sub 180 temps makes me second guess everything.

 

Since this thread has helped me out a ton in figuring out what to do, I figure I’ll reply with what I did. I’m pretty sure I installed everything mostly correctly lol!

A little background: I’m checking what I’m very certain (99.9%) is the trans pan temperature on a scan gauge 2. I’m lifted with 255 85R16’s. I noticed that a regear helped my transmission temperatures a little when driving on roads in the 40-55 mph range. However; in dirt roads the temps would climb to 185-200 very easily or on highways when climbing up grades and when the ambient temperatures were hotter.

Then one day driving in central Nevada going through some steep grades (both paved and dirt) my transmission temperature rose to 220 on a steep dirt road. On pavement the tc was unlocked 3rd and 2nd gear driving up the switch back roads. Luckily it cooled down quickly but it never got below 190 (near the operating temp of the engine coolant which ranges from 190-195).

To remedy this, I ordered and installed the Hayden 698 and Iconic Fabrication bracket. I Installed the bracket this way in order to avoid pinching transmission lines or having too tight of a radius of the lines.
My major concern is perhaps I have too much hose “exposed” and as precaution I used some heater hose for some abrasion protection. I’ll probably end up ordering some nylon sheathing for the lines for additional protection. I routed the line from radiator return line to auxiliary cooler and then back to the transmission. So I still use the radiator the initial warming and cooling.



The kit was helpful and I didn’t spill too much fluid which was collected and measured. I added approximately 1/2 quart of Mobil 1 3309 (heck even the bottle looks like the T-IV I’ve bought from the dealership in the past)!

For the most part after the install, my transmission temperature ranges in 140-160 range. The hottest I’ve reached was 172 but that was climbing a very steep grade paved road where the transmission stayed in 2nd or unlocked in 3rd gear for most of the time. But then on the downhill it quickly cooled down. I am very impressed with the cooling abilities and wished I installed this earlier!

Obligatory truck picture of course!


PS the truck is a 4 cyl. with the 4 speed automatic transmission and 4x4 (A340F I think). Installation was very simple on this pick up.

 

Thanks for all the info in this thread and a couple others I'll be installing a cooler very soon. I hit 230 degrees on the transmission while towing in the summer heat.

I have a 2021 that only uses the radiator as it's trans cooler. Does anyone have a picture or drawing of the radiator for the newer Tacoma's, more specifically which lines are from transmission. Trying to dummy proof this for myself before taking apart some hoses

 

This diagram illustrates the AC 60 series, 6 speed transmission found in Toyota, Lexis and Subaru vehicles.

 

If, IF, the rads are the same for the non-cooler models as the models with the cooler, you will find the trans lines enter and exit the rad on the drivers side. The upper line is from the trans, the lower line (straight down from the upper line) is the return to the trans.

 

I thought the bottom was the pressure and the top was return, can anyone else confirm?

 

From what I found, and what that diagram above shows, it runs through rad before it runs through the OEM cooler. Top runs directly to trans tstat, bottom routes to the cooler.

 

My findings were different. Disconnected the hoses to the hard lines that run to the transmission, with the truck on, fluid was coming out the hard lines to to the hose that ran to the bottom making me believe the bottom was the pressure line. I’ll have to check again this weekend, may have gotten them mixed up.

 

To satisfy my thinking I spent a little time searching for a definite answer to flow direction.
The diagram that I posted above is for the AC 60 series, 6 speed transmission.
While doing my search it was indicated by @gearcruncher (in the link below) that the transmission in my 07, 4.0 Prerunner is the A750 E series 5 speed transmission. There is also the F version, which is for 4 wheel drive vehicles.

https://www.tacomaworld.com/threads...th-pics-for-second-gen-4-liter-trucks.289913/

I'm not sure of the transmission that @DannyD has so these diagrams showing fluid flow may be all for naught.

Did I find a definitive answer? I'm not sure, but I know a little bit more about the transmission that's in my truck.

Maybe @gearcruncher will chime in on this.


I found this on another forum. Link below.

https://www.toyotanation.com/threads/transmission-oil-flow-general-question.1703331/






https://www.transmissiondigest.com/diagnosing-a750e-f-2-3-flare-after-overhaul/

 

I have a 2021Tacoma Sport, v6, 6sp, short bed.

Trans oil connections are on the driver side, just like the photo in #346 and the TOP Trans oil hose was noticeably ALWAYS hotter than the BOTTOM hose at the radiator - per the post at #346 when checked at idle. The post in #350 does not show the Thermostat.

Why would the TOP hose be the return hose if it has the hotter oil returning to the transmission?
I was concerned about the lack of an additional external oil cooler.

I mounted the

$52 Hayden 678 Universal Rapid-Cool 9.5” x 11” Add-On Transmission Cooler – Not for Direct Replacement of the OE Cooler

Hayden 678, using the Hayden hose, from the radiator/trans oil BOTTOM port to the top connection inlet of the Hayden then spliced with a 3/8" double barbed brass connector the bottom outlet into the original line (bottom hose) back to the trans.

Radiator bottom port to Hayden top inlet;
Hayden bottom outlet to brass barbed connector to original bottom return line to trans

I have great results with pinned THERMOSTAT.

May 5, 2024 -1hr 50 min, 111 miles, Engine coolant 198F, PAN 158F, TC 158F, Outside ambient 86F, Speed 53 mph.

June this year at Grand Canyon=4 hours driving, 250 miles, Engine coolant 190F, Pan 142F, TC 143F at 66 mph, Ambient outside temp 42F.
When sitting parked, TC increases 10 F above Pan temp.

July 12,2024 - 6 miles, 13 minutes driving, Engine coolant 198F, PAN 155F, TC 167F sitting at stop light left turn lane, Outside temp 107 F.

TC temps will be appx equal to PAN when driving and rise when sitting.

Seems a pinned thermostat, with an external cooler works well in the desert environs.
Have many other trips with similar results.

 

@gearcruncher - Can you confirm the flow on the tacomas with the internal cooler? Line going into the bottom of the radiator is high pressure while the top is the return? or vice versa?

 

Another screen print. Today.

Its about 100F outside. Engine at operating temp. Freeway driving. Look at TF1 Pan and TF 2 Conv temps. Waiting at a light, TF2 can get 10F hotter.

 

My 2007 4.0 SR5 quad cab with tow package was getting really hot. Even cruising up nearly imperceptible grades on the highway on hot days I’d get pan temps >200 and TC >225. Off-road, high altitude desert in 4x4 it was getting pan temps of >220.

After reading through all of the cooler threads I could find I went with the TRU-COOL LPD 4590, in series with the radiator, to get maximum cooling.

But now I think the cooler I got may have a defective bypass. It’s cooling way too much. The pan won’t go above about 180 and in the mornings when it’s about 70 outside it takes 15 minutes of driving to break 100. I don’t want to trade one problem for another so I need those pan temps back to a good range (sounds like that’s about 170-200 but open to inputs).

Is this a common problem with LPD4590, or did I get a bad one? @gearcruncher , I know you’re a LPD fan. Any advice?

 

@afcope, after a quick "google search" (for me the the TW search results are too wide and varied) I found this post from @gearcruncher that my help answer your question.

https://www.tacomaworld.com/threads/normal-transmission-temp.325212/#post-8527863

 

Thanks @BlkDakDave. To clarify though, my question was more about Tru-Cool LPD coolers over cooling when in series with the radiator.

I suspect the bypass on my cooler is defective. Today, the radiator was 195 but the trans pan never broke 125 after a long commute, according to my OBD Fusion.

 

If you're ever concerned about which line is a transmission line, it literally says "AT oil" on it.

 

I can't speak to any defective cooler unit issues, but that is a GOOD size cooler.

Sounds like you're running with the t-stat pinned? Were you towing anything?
That TC LPD 4590 has a 28,000 GVW with a 24,000 BTU.

My

$52 Hayden 678 Universal Rapid-Cool 9.5” x 11” Add-On Transmission Cooler – Not for Direct Replacement of the OE Cooler

Hayden 678 has a 18,000 GVW - BTU ??? But for up to 5,000 lbs towing.
The TC that would be my equivalent would probably be the TC LPD 4588 - 19,000 GVW with a
14,400 BTU. That's about 2/3 - 66% of what you have.

Here are some Screen Prints at appx70F running temp with about 600 lbs in the PU for camping. Not towing.





Notice, these are for a PINNED t-Stat with the Hayden 678. (I would expect similar result with the TC LPD 6588 if I chose that one.) The cooler is run in-line/series with the radiator cooling.
I could increase the temps by 10F if I put on my cardboard wrap/block in front of the cooler and I did so this past winter. It was about 3" wide - full height of the cooler and blocked I'd say 40% of the cooling fins. Seemed to work OK - That's how I know about the 10F temp increase.

Did you try putting a cardboard blocker in front of you cooler?
Comparatively, That TC LPD 4590 is a GOOD size cooler.

 

Thanks for the reply @Tacogent. I have a gen2, so no thermostat to pin. That LPD4590 is a beast, especially since I am not towing regularly. It's about 4x the surface area of the stock cooler:

But I got it because it's supposed to bypass when cold, so you shouldn't be able to overcool. I did slap a piece of cardboard over it in the morning and it mitigates the overcooling problem...but I'll need to add an external bypass or replace the cooler to get a sustainable solution. That sucks...

Thanks for the comments and pictures

 

Very suspicious of your 125 F number. That cooler is designed to bypass until ~170 F. I'd get an IR thermometer on the inlet an outlet of the cooler for sanity sake. Does the OBD fusion require any math or manual parameter identification to read the trans temp?