Install complete on additional transmission cooler

@JohnLakeman

As you mentioned earlier, if the thermostat is pinned, the amount of heat dumped into atf by the puck may not be that significant since the atf cooler/radiator is dissipating a lot of heat at the same time ...

Without any major study or thermodynamics analysis or field test, we don't know the exact impact. for me it was just another "feels good" kind of thing by thinking less heat being dumped into atf ....

once you are at the operating temperatures and the engine and atf have warmed up, with the puck in there and the thermostat pinned, atf cooler/radiator will be somewhat helping cool off the coolant because the heat transfer will be from the coolant to the trans fluid. Kind of like the intended "atf warmer" that you no longer need or want. lol

 

Not clear on what you're saying, but in the OEM configuration, once the transmission fluid temperature exceeds the coolant temperature by one degree, heat will actually begin to flow from transmission fluid to coolant, ergo...then it's a "cooler". The heat from the transmission fluid is then warming the engine coolant, but the amount of BTU transferred is minuscule compared to the cooling capacity of the radiator, so there is no change in coolant temperature, and not a whole lot of change in the fluid temperature either.

 

What I'm saying is if the thermostat is pinned , heat transfer in the puck will be from coolant to AT Fluid. Because after operational temperatures have been reached, the coolant temp will in most cases be much higher than ATF temperature. This is for the engines with the traditional atf cooler/radiator. Pinning will result in the atf cooler/radiator to be always in the loop and typical atf temperatures of 140-170F whereas typical coolant temp is 185-197F.

As a result, removing the puck by bypassing it, will prevent additional heat transfer from the coolant and will result in even lower ATF temperatures.

Edit:
I don't have my excel sheets handy but the trans fluid temps will approximately be in that range (140-170F) maybe as high as 180F but definitely much lower than the coolant temp.

 

This is entirely my point.

The puck cooling is only as effective as the the engine temperature will allow. If the engine is running at 198 degrees, thats all the puck cooler can provide to the ATF... and the remote/air cooler has to fight against it.
If the puck is bypassed/removed from the loop... the remote/air cooler will only be as good as the BTU's it can provide... but (if large/effective enough) should be able to pull and maintain ATF temps BELOW the engine coolant temps.

 

What are you two bar room engineers waiting for?...End debate on how heat transfer theory works, bypass the "puck", and get on with enjoying the results.

 

Pretty interesting back and forth in this thread, I like it.
I have an 09 Tundra with the OE cooler mounted behind the grille. I pinned my thermostat because I noticed trans temps as high as 250° while off-roading in technical areas. Very low speed high load. (I use OBDFusion for engine management). Pinning the thermostat resulted in daily driving temps of 165°-180°. Although the trans still got up to 245° in technical off-roading sections while my engine/coolant temp maxed out around 205° .
I think bypassing the heat exchanger/puck probably won’t reduce the temps in those conditions by much if anything?
Any thoughts?

 

You are correct. Under your technical off-road section where you observed 245F, the puck would actually help cool off the ATF. Because your coolant will be much lower @200F +/-
Under this situation, heat will be transferred from ATF to Coolant in the puck. as far as how effective this "cooling" will be is subject to debate due to the size of the puck. Under these situations , I would not recommend bypassing the puck.

However, if you were doing normal driving and towing and no technical off-road, then you would never see atf temps that high and bypassing the puck should help. I have yet to see my atf temp go over 180F it's typically in 170's but I don't do technical off roading where the torque converter is UNLOCKED and there is not much air flow (due to crawling rocks and hills at a very low speed and low rpm). That is one of the worst case scenarios for atf temperature.

Btw, I haven't bypass my own puck either at least not yet. Waiting to collect more data and figure out how effective it is in heating or cooling.

The 2019 and up guys with no trans cooler/radiator complain that the puck is not effective enough to cool off the atf. These are the models that Toyota I think started saying that the "ATF Warmer" is also a cooler. Technically Toyota is correct but the amount of cooling and it's effectiveness is subject to debate.

 

My feeling is bypassing the warmer/cooler puck would have a very small gain and not worth the effort. There just not enough of a temp difference. Let say coolant is running at 200 and trans is running at 180. ATF flows to the puck first and picks up some heat but then heads off to the ambient cooler. The small amount of heat collected from the puck is removed.

 

Your transmission heat load in technical off-roading is apparently well beyond what Toyota specified for their design.

Have you considered retrofitting a larger aftermarket heat exchanger in place of the OEM cooler? I wouldn't bother with a series installation as in this thread. I would just buy the single biggest area, highest BTU rated, most efficient (stacked plate, or plates/fins) exchanger you can find. The

$216 B&M 70274 SuperCooler Black Aluminum Fluid Cooler

B&M 70274 featured in this thread is stacked plates, 13" X 11" X 1.5", and is rated at 29,200 BTU/hr. Derale has a stacked plate exchanger rated at 37K BTU/hr, but I'm a little bit skeptical of that one. Either of these exchangers is probably suitable for a big motor home.

 

You might be right, the load in technical stuff could be more than Toyota designed the cooler for. I’ve considered replacing the OE cooler with a bigger one but wondered if the temps I’m seeing are normal per Toyota.
I heard the trans thermostat doesn’t even open until somewhere aground 225°. Not sure if that’s correct and I haven’t tested it but it’s a higher temp than I was ever comfortable with in other vehicles.
I also don’t know what the Toyota WS trans fluid is rated at. Is it designed to handle temps in excess of 250°?
Anyway, I may eventually replace the OE trans cooler, I replaced the OE PS cooler with a custom setup.

 

Thermostat opening temp has been discussed in this thread. Some say 200*, and the thread OP said 245*. I believe the 200*, I don't believe the 245*. The 225* sounds reasonable, but needs to be checked. If the OP's thermostat was actually not opening until 245*, it had to be a faulty thermostat. In your case, opening temperature is not a factor, because you've pinned it open and saw little improvement.

Toyota's WS fluid is a blend, not a full synthetic. I would be very uncomfortable running WS at 240* for any period of time, and would implement a program of watching condition closely and making frequent changes. For comparison, one well-known full synthetic transmission fluid reportedly begins degradation at 280*, and rate of degradation increases rapidly as the temperature increases.

Dude...that's the PS cooler? You are generating some serious heat if that is required to do the job on PS. I think that is the Derale I referenced above (Series 10000, 19 plates, 37KBTU/hr), or maybe next one down (16 plates).

 

All this talk about bypassing the puck an no-one has mentioned an aftermarket thermostat to help lower coolant temps?
URD USA has them for the Tacoma 1GR's at 170F and 160F. If only there was an option for the 3UR.

As for thermostat opening, I originally believed it was 225-245 like the OP.
The reason why is i could watch my trans temps climb past 225+ until suddenly they would plummet down to 190.
I assumed that this rapid temp drop was due to the thermostat opening and allowing the fluid to cycle through the trans cooler.
Since all OEM's try to squeeze every MPG drop out of designs, i chalked up running hot as Toytota minimizing para-static drag
If the thermostat started opening at 185-200 as people have stated, why do the temperatures climb that high then suddenly plummet?
Clearly the fluid to air heat exchanger is capable of rapidly dissipating heat. Are there stages to how much the thermostat opens?
This was all observed towing in 4S with torque converter locked on a hill.

 

No one makes an aftermarket transmission thermostat for the tundra. It’s a specific part that I doubt anyone would try to make. Mine opens around 195. If i get in that range, the hoses going to my cooler are warm. Since it s a wax, it might not be fully open but it is doing something cause that’s where my trans temp will settle too.

Edit: NM. I misread and thought you were talking about trans thermostat. I read a lower engine thermostat is actually harmful for daily driving and only used in racing.

Here is one. Says it is 160 vs factory 180.

https://www.mishimoto.com/toyota-tundra-2007-low-temp-thermostat.html

 

There are universal thermostats, but you must have lines that connect directly to the transmission.

All this talk about bypassing the warmer/cooler is just that...talk. I've tried to tell these guys three times that "bypassing the puck" on a 5.7L A60 transmission is mechanically impossible for mere wrench enthusiasts. If you happen to be an experienced, skilled machinist, you may be able (with good design skills) to modify the transmission case to "bypass the puck" and thermostat, and run fluid cooling lines directly from the transmission case to a heat exchanger behind the grille. You could even install one of these universal thermostats in the lines. Thermostat below opens flow to cooler at 180*.

https://derale.com/product-footer/fluid-coolers/thermostats-1/fluid-control-thermostats/15719-detail

 

I need to figure out when the trans t-stat opens just so I know. I don’t plan on running it pinned all year.
I’m not comfortable with the high trans temps either but don’t know the specs of WS. I‘ve done a complete fluid swap twice now with 135k on the odometer.
I don’t know that the PS cooler I have is required but I had to relocate it because of my bumper. The OE PS cooler is huge but less efficient so I went with this one.
Hayden Automotive 777 Rapid-Cool 37mm Heavy Duty Engine/Transmission Cooler

$96 Hayden Automotive 777 Rapid-Cool 37mm Heavy Duty Engine/Transmission Cooler

https://www.amazon.com/dp/B0049ESKSM/ref=cm_sw_r_cp_api_i_ek0kFbT4KWZWJ

 

Ah, yeah. That

$96 Hayden 777 Rapid-Cool 37mm Heavy Duty Engine/Transmission Cooler

Hayden 777 looks identical to the Derale I mentioned earlier. What I've found is there must be only a couple of manufacturers for these engine/transmission oil coolers. Certain models of all brands Derale, Hayden, B&M, Tru-Cool appear identical to me.

 

As @jc153 has observed, his atf temps were about 250F before pinning and while doing technical off-road.

After pinning, he was seeing 245F. so there was not a huge difference. However during normal driving, the atf temperatures are significantly reduced to 170-180F if the thermostat is pinned.

I discussed the above (high load / low rpm) in a PM with one of the members here. Either with op or another member (Coryb87?) who is very knowledgable.

I am not knowledgeable when it comes to auto trans design but my theory was that at low speed and high loads, the atf line pressure is very low and not much fluid is pushed around through the lines and to the cooler/radiator due to low rpm so you will see much higher temps.

Also a lot of times people see high atf temperatures and they attribute that to thermostat not being open. However, the thermostat could be open but due to low line pressure (low rpm), you may not see the impact immediately ... and as soon as the rpm goes higher (e.g. By shifting to S5 or S4), then fluid pressure goes up and cooling will be more effective.

That's why iirc Toyota and many others suggest towing in S5 or S4. Not only the rpm will be higher in s4/5, but the chances are that the torque converter stays locked and you basically kill two birds with one stone.

Or maybe higher rpm, pushes more hot fluid over the thermostat and forcing it open sooner than later. idk. But all I know is that rpm has something to do with it.

This however won't help @jc153 situation since his rpm is low with TC unlocked.

Edit:
I do the following test on one of the hills near me.
without pinning and in S6, I've seen that my trans temp creeps up slowly to over 200F to 224F and as soon as I downshift, the trans temp drops to 187F or so (the coolant temp). But under same situation if I leave the trans In S4, it never exceeds 195F or 200F.

 

The ATF cooler in front of the radiator is not working unless air passes through it.
Something with a fan mounted to it would work better... or like in the old days... the cooler was ziptied right against the center of the radiator so the fan could pull air through it when not moving.

With the OEM unit mounted some distance from the radiator and offset from the fan, it really isnt working all that well unless you are moving air through it by driving down the road.

 

Yes, I know people who added their own atf cooler/radiator and fan.

 

Sorry, I also just realized that you were talking about the engine coolant thermostat.

The issue with trying to get fluid cooling by lowering the coolant temperature is that you're only going to increase the temperature differential by maybe 40* at best, and you're still stuck with a "cooler" with small heat exchange surface area. As the fluid temperature surpasses the coolant temperature, there will be increasing heat transfer to the coolant, but, imo the small surface area still won't allow enough heat transfer to help much.

Btw, thanks for the feedback on your thermostat operation. I've been trying to understand how the thermostat works. A sudden drop in fluid temperature suggests that your thermostat is opening fully above 225* to drop the fluid temperature to below some set temperature, where the thermostat closes completely. The cycle repeats when the fluid temp reaches 225* again. I was wondering if the transmission thermostat opened partially to maintain the temperature set point.

 

@TTund16 No problem. I agree, not major temperature delta gains with lower coolant temps.
Aside from the transmission benefits of running in S4, higher RPMs can actually reduce coolant temps since coolant flow rate is directly proportional to RPM.
A higher flow rate increase the ability to pull heat out of the block.

 

You’re right about the pinned trans T-stat keeping daily driving temps much lower, lots of air moving through the trans cooler. I do think the TC locking has more to do with the trans temp than the line pressure though.
I have an OVTune and the TC locks in 4, 5 and 6. I have a gauge that tells me when the TC is locked and temps drop instantly when the TC locks up at any rpm.

 

The other issue is that a lower temp (engine coolent) thermostat will probably throw a code and trip the check engine light.

I think if someone wanted to get really carried away... they could put two coolers on the truck.
One to cool the antifreeze before it enters the "puck" and another to cool the ATF.
If both had a fan mounted to them, they would do a better job at low speeds or rock/mall crawling when there isnt a lot of air moving through the grille.

 

Your comment is speculation based IMO. I am running a 170 degree thermostat in my Tacoma, no issues, no codes. truck ran 190 prior to mod.
I modified everything short of a supercharger on my Tacoma to make it a tow rig. Ultimately, i made the decision to do the Tundra mod.
If you deleted the coolant thermostat all together, it would likely throw a code
The downside to over-cooling the engine is that the ECM would be tricked into thinking the truck is in warm-up mode and never reach operating temp.
Since the Tundra runs hotter than the Tacoma (200f vs. 190), dropping the coolant temp 15 degrees or so should have no impact on how the ECM reacts to inputs.
DISCLAIMER: that is also speculation, if a kit was available i would be willing to test and report back findings.

 

https://www.700r4transmissionhq.com/p0128-toyota-tundra/

If a colder thermostat could be run without causing problems, I think it would be great.

Use to be years ago you could buy a 160, 180 or 195 degree thermostat for damn near anything.
Sure would be a handy option for our trucks.

 

Lower thermostat kit? Post 193.

https://www.tundras.com/threads/ins...transmission-cooler.12385/page-7#post-1855063

 

The article you cited states thermostat failure and/or wiring sensor failure is the root cause for 90% of the reason codes are thrown. A stuck open thermostat is the equivalent to thermostat delete. Neglect for basic maintenance creates the potential for thrown codes regardless of stock or modified.

 

That mishimoto one says it opens at 160. Is that too cold for daily driving? Good for towing? But who’d want to change their thermostat every time they towed. Would the truck see 160 as too cold and throw that code? Driving in the desert vs Alaska?

 

I think 160F is considered warm engine ... the obd app thing in one of my other cars announces that every time. it says something like "Engine operating temperature has been reached" lol

 

yes, TC is a killer and not very efficient and produces lots of heat.

I need to look into ovtune. I know some people have programmed their scangauge and ultragauge to show TC locked/unlocked but I couldn't find the code.

I assume TC is not locked when you are crawling rocks. Is it?
Can you keep or force the trans in 2nd gear (S2) & Locked using ovtune?