Pinning open cooler stat

So to branch off all the cooler talk- why is everyone pinning the stat open when they put on a cooler? Then why have it? Does or can operating "too cool" or "cold" cause issues?

 

I, too, am curious. Thanks for asking.

 

Some are obsessed with running cool. This is a Goldilocks scenario. You wanna be just right. Too cool and the shifts aren’t as smooth and the transmission isn’t as efficient. Too hot and you burn the fluid. WS is rated for up to 285° or so operating temp per Toyota. 185-200° is the sweet spot for these. 220° won’t hurt anything, 250° is getting pretty warm. I never saw anything over 250° when towing heavy so I didn’t worry about it.

 

Ok, won't change a thing then. Thanks

 

Because a cooler trans is a happy trans. <This is when the Toyota engineers will step in and argue.>

I have ran mine pinned open for a couple years now.

mine will run at 175 most of the day.


on cold days*, it will get to 120 quickly....see, the engine is still warming the trans via the puck.

it will never ever get too cold.

for most, if not all situations....I will run an 80degree delta between pan temp & ambient.

on 100 degree days here in Houston...I will cruise at 175 degrees.
you will cruise @ 185-195 with the cooler unpinned.
if you don't have the cooler, you will be ~220-230 degrees
i know...I lived it.


I do not want my trans running at 230 degrees unloaded....that ain't right....never has been.

I also have a 9psi Harrop S/C...so I can, at any given time, put a LOT of heat into the trans.
I would much rather start at 175 degrees than 230 degrees

Cooler trans does not affect, in any way, your mileage.
I know, I watch mine daily. I avg 17mpg. yes, I really do. I drive like I'm 102 yrs old.




*if you live in a frigid location....you might not want to pin open in the winter.

I live in Houston...we die if it gets below 50 degrees.

 

Ohio here so we cruise anywhere from -10 to 100

 

-10......yeah.

Don't pin it open.



I am always amazed at how humans survive in that weather.

 

I like the 4 seasons, taste of everything throughout the year. Kids and I love the snow, wife is questionable. lol

 

Two points I want to make.

1. this was not a troll post. I am genuinely interested as a recent 2020 purchaser.

2. Again- why would you even buy and put a stat in then rig it to stay open? Seems like a waste of time and money.

 

Application specific I would say. Live in hells butthole, have a supercharged truck, tow over the limits etc.

 

1. I too own a 2020

2. so that it runs cooler. when the thermostat is unpinned, it will let the temp climb to 185-195. which, I suppose, in some circles, is fine.


my contention is, can I make it cooler? yes. pin it open and it will run thru the cooler at all times.

 

Quick question - I just purchased all of the parts to add a transmission cooler (Hayden) to my 2019. It’s got 112,000 miles and I figured for longevity sake I might as well do some preventative maintenance, especially before I start towing the rpod around the states. So if installing an “external” cooler do you still recommend pinning it open?

 

as @KNABORES stated so well.

application specific.


for fun...get a temp monitor and decide for yourself.

 

If I had a 2019-2021 and was adding a cooler I would not bother to install the thermostat, I’d get these fittings in their place and leave flow to the cooler 100%, part number courtesy of @Mdl. You can’t/wont run your transmission “too cool” by having the cooler in play at all times. Especially if you’re leaving the warming puck in place that warms up the fluid anyway. I recommend this video by WAT who rebuilds these transmissions and offers valve body upgrades for them. TLDR, you can’t run it “too cool” and borderline getting too hot is basically the temp range that the thermostat opens. https://m.youtube.com/watch?v=DyU3LIpA-Mg&pp=ygUYd2hvbGVzYWxlIGF1dG9tYXRpY3MgZmFx

 

yeah I have a scan gauge 3 and was monitoring temps unloaded. Went to the mountains this weekend and with nuts myself, wife and 17 year old daughter in the truck with minimal supplies I was running 240 degrees. Hopefully getting around to installing the cooler next weekend.

 

@Silver17 gave a ton of good information there. I'll add the missing link to directly answer: Because the t-stat gave you the ports needed to route trans fluid to a cooler and back. That's why it was needed, until @Mdl figured out the LC elbows.

Plus, not everyone needs/wants to pin or remove completely, but there are lots of options now. If you don't care about warming the trans fluid to temp quickly, you can remove/bypass the warming puck, which now allows you to use the elbows. A few of us have purchased aftermarket inline & serviceable thermostats so we can better tweak and tune our temps based on needs. The factory t-stat is probably plenty of 80%. Pinning is good for another 10%. That last 10% are typically the power adder crowd being unkind to their drivetrain in multiple ways.

Not right, not wrong, just multiple ways to skin a cat. Not really different from the 2-bucket wash method vs automatic carwash debate, the blower motor upgrade discussions, or (forgive me for saying it!) the oil weight debate.

Edit: for me, I've added the cooler and t-stat, still see up to 220 when towing for long durations, and want lower so I'm not feeling like I need to change fluid every year. I also want the added clearance down on that side of the transmission, so I'm removing everything and replacing with elbows to give even more clearance for the turbo plumbing. Modding is an addiction (or is that a hobby?)

 

‘21 owner here with an aftermarket cooler and OE t-stat. I pin the tstat open when towing in the summer months (VA/WV). Other than that - the tstat is unpinned. I did test the tstat pinned in the winter months - but it seemed to take the trans a long time to come up to operating temp (monitoring with SG3) - so I nixed that idea.

 

It doesn’t make any sense to install it and bypass it but people do weird stuff all the time.

 

The point of the thermostat is simply to allow the fluid to get up to operating temperature as quickly as possible, once the fluid is up to temp the thermostat pretty much stays up the entire time, all pinning it does it keeps it cooler longer. Not a big deal in the summer time but in the winter you want that fluid to get warm before driving if you can, that's what the warming puck is there for, it can get the fluid up to about 60° in 5 minutes in the winter, my guess is that would not be the case if you left it pinned.

 

Damn, this thread is insightful... I'm gonna try and pin my thermostat... Since my transmission fluid remains hot over 12 hours of sitting, it does get hot as balls here.