Transmission thermostat pinning part way

I've read several posts about transmission temps and some discuss pinning the thermostat open.

When I do pin fully open it often runs a bit cooler than seems right, anywhere from 135-165, mostly depending on the weather. And only a few degrees warmer when towing my 3000# trailer, which I tow a lot.

After thinking of ways to partially open the thermostat I finally stumbled on a neat trick. When not towing the pan generally runs about 170-175, when towing about 175-180. It used to run about 15+ degrees warmer when not pinned.

I cut a Hitch Pin Clip, see pic, on the big circle part and stuck the uncut end through the top hole of the pinning holes. I pushed in just beyond the first curve of the pin and it held the thermostat plunger from fully closing, though it is very nearly fully closed. My first attempt held about 1/2 open, and it ran a bit warmer but still cooler than I preferred. It seems that even when the thermostat is fully open, like going up or down a long incline the pressure of the thermostat plunger keeps the pin in place.

I do also run a tranny cooler that opens up at 185, but was still getting the above cooler temps when fully pinned open.

I gotten lots of useful info on this site... so thought I would share my lucky find.

 

What's wrong with fully open lower temps? Lower temps do a,better job protecting the internals and fluid longevity?

 

There's def a preferred/optimal operating temp due to viscosity at temps. It's why some cars may feel a bit odd shifting when first driven in the cold.

I have no idea what that temp is for the Tacoma, but I rarely tow.

Also what's up!? Another Ga boy

 

I think you're looking for a solution for a problem that doesn't exist. If you have wildly different temps with the Tstat pinned vs not pinned when everything is warmed up then you have a faulty Tstat.

 

Howdy, from ATL, Our transmission thermostats are set to pen at 190. transmission longevity can be correlated to fluid/operating temperature. Failure rates decline the colder the climate according to Next gen transmission data. (aftermarket transmission parts provider)

Pinned thermostat with stock cooler and my trans temp gauge is around 160 max but i also dont tow very often.

 

You can also put a larger cooler on here if you're worried about temps and/or your truck didn't come with one (mid-2020 forward). There's a good thread on here about adding one.

I don't tow and mine still has a cooler and I can tell you my pan temps stay pretty stable but the tc spikes a bit (220-230) on heavier inclines and once fully warmed up. This is pretty short lived though. The other mitigation you can do is more frequent drain/fill on your ATF.

 

Do you guys really think you are smarter than the Toyota engineers that designed the transmission cooling system?

 

yes because my main goal is reliability. Their goal is designing to meet efficiency goals and making it out of the warranty period.

 

That sounds like paranoia based on no evidence to me.

 

Apply some critical thinking: What happens to transmission fluid longevity as the temp increases?

 

I have a medium sized extra cooler on mine. The basic minimum temps are more controlled by the tstat than the cooler. The cooler helps keep the pan temp from rising as quickly when on long inclines, and cools down significantly quicker after a long hill. But on 80-100 degree days towing on level ground the pan is/was 195. which is about what some Rams run without a load.

I don't particularly mind the tc spikes, as they are temporary. But did want a general running temp a bit closer to 175-180.
I don't have a scientific basis for that temp range. It is based on info showing more than 185 the life of the atf doesn't last quite as long. And some articles that suggest 140-150 is a little too cool for most transmissions, though they did not suggest it would damage the tranny.