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

Some of the bypass style coolers just use smaller internal passages in the larger portion of the cooler. So that when cold and thick it flows easier thru the upper portion of the cooler since passages are larger. As the fluid thins as it heats up it can then flow more thru the lower sections. So its never a 100% bypass.

Other use and actual bimetal thermostat plate/tab that block the flow until it reaches a certain temp.

I wanted more control over the cooling from the add on cooler so am using an actual oil thermostat that only opens when temp reached 180F.

So until it reaches 180F its just using the original factory ATF cooler. With this setup I have never seem temps higher that 175F and lows around 140F during the winter.

I have the 750F trans in my 2015

 

I have one of those units I am installing.

 

Even these real oil thermostats are not 100% bypass. When closed they still allow 10% flow.

From product description " At temperatures below 180° F the valve is open with 90% of the oil bypassing the cooler while the remaining 10% of the oil flows through the cooler. This maintains constant system pressure, preventing air pockets and eliminating cold oil shock"

On a previous vehicle i installed the same cooler I had without a thermostat. After heavy traffic on a 90+F day I got home and checked the fluid temp using the dipstick (remember those ) and it was barely warm at all. I knew when winter rolled in it would be way to cool so next was the thermostat install.

 

And IMHO the the concept of the in radiator ATF line as being used to warm up the fluid is incorrect at least in the case of very cold temps where you would think it was designed to do.
If its very cold (say -4F) and you are moving so there is airflow then the coolant in the rad isn't going to be very warm at all. If the rad has the capacity to cool the engine at 90F then its barely being utilized at very low temps.The engine thermostat will barely have to be open to keep the engine at operating temp.
So at really cold temps I can see the in rad atf line as being a cooler. And seeing that the in rad line is located on the other side of the radiator than the coolant input line from the engine its even cooler that what being sent to the rad from the engine.

I like the concept and the idea of having the ATF thermostat located in the transmission itself as long as the actual ATF cooler that is used has sufficient capacity to indeed keep it cool.

If i was to redesign the system I now have I would eliminate the radiator cooling line and run the fluid thru a true thermostat and then a decent cooler. This should serve to bring up the ATF to a proper temp quickly and keep it at a very tight temperature range.

 

@babylon5 that's the path I am going to take. I like how cool the 4590 keeps my transmission even when it's 115F, uphill, in a headwind...I just need a bypass for when it's cool. Thanks!

 

Hmmm.... If I didn't have at T-Stat, I'd probably do the same !!! I know I could reroute the Trans oil lines now, but for ......1) springing for a TC 4590 and a Derale fluid control thermostat, ( $100.00 + and $70.00 respectively), something like those bucks $$$ and 2) all my additional labor, I just might've just done/do it!
I think your reasoning is sound.
I can't see any conflicts in your automobile logic ...
Buuuttt, ...... I'll work with what I have ....

Look at that face !!!

 

Now in the 40+ years I have been driving I have never seen it happen but with the atf coil in the radiator there has been the odd mention of the dreaded pink milkshake where the line corrodes and coolant mixes with the ATF. So if you bypass the rad all together you would never have this to worry about. If i ever had to replace the radiator I would just go for one from a manual trans model and skip the in rad atf cooler altogether (running a real atf thermostat and decent cooler alone).

 

The AT models only started doing this around 2020 or so. You'd be fine with your 2015.

But also, regarding the dreaded milkshake

See "Nissan Frontier smod, 2005-2011"

Talk about bad design




Speaking of the 19 plus hundras run a line with coolant through the transmission housing to cool the transmission instead of the other way around. I'm surprised there haven't been more problems with this, but I'm guessing that engineering is solid since it's been 5 years since they started doing that and we haven't really seen problems with it.

 

Is that picture at Berlin, NV?

 

It is! Good eye!

My wife and I take truck camping all over Nevada when we have the time. Although when we went Berlin-Icthysaur, it was hot, so it was a day trip.

 

Berlin-Icthysaur State Park ??

Goodness --- where is that? As an Amateur Astronomer in SE AZ, --- I think that is a Bortle 2 dark site ?

Been there at night?
https://parks.nv.gov/parks/berlin-ichthyosaur


That is a very interesitng Nevada State Park!

Ever consider get it an Official Dark Sky Observing Cert?

https://www.npca.org/articles/1806-see-a-sky-full-of-stars-at-these-certified-dark-sky-parks

 

That’s correct! I didn’t know about any of that besides Great Basin and Death Valley being located in some dark sky country.

Berlin-Icthysaur is very unique. I love central and eastern Nevada. My wife and I will probably return at some point as we didn’t spend enough time there I feel like.