Pinned Trans Thermostat observations

Towed the rzr in 97* heat. 70mph in s5 through the hill country. Saw 206* in the pan. Unpinned.

 

My 2021 is usually 220 degrees plus or minus 10 driving on the flat freeway. Supercharged with 35s no trans cooler. With my rebuilt transmission I am going pinned, trans cooler and 20 degree lower engine thermostat too. Will be curious what the results are.

 

I asked if 150-170 was OK as that was where my temps were at over the winter. He mentioned not to be fixated on pan temp and pay attention to torque converter temps.

 

It stands to reason at least that if the fluid in the pan is cooler before entering the TC that it will also be cooler at/leaving the TC though, no?

 

Yes. I don't know if he gets a lot of questions concerning pan temperatures but kinda laughed when I asked what's a good temp to shoot for. Too many variables I guess just don't cook the oil.

 

yes, this.

I would rather have cooler fluid entering the TC, than hot fluid.

Hot = >195degrees.

pinned, I send ~170 degree fluid into the TC....all you unpinned fellas are sending ~200 degree fluid to your TC.

and, as mentioned before, I would prefer to have AVG 175degree fluid, than AVG 200degree fluid.

why? cooler is better. hotter is worser.


Now, does it matter? yes. Heat, as for back as the antiquity days of Transmissions, has ALWAYS been the enemy.
We still use multiple flimsy friction plates. keeping all those plates as cool as possible is the key.

is it OK to run unpinned & see 210degrees on flat unladen roads?
probably, but why do that when all you have to do is bend a damn paperclip and pin your trans open and see 170degrees.


and for all the contrarians that are going to comment on the fluid being too cold....impossible.
the puck heats the damn fluid.
mine gets to 120 in about 5 minutes. 160 in 15 minutes.

and when is the last time you watched your trans fluid heat up & then compared it to an pinned application? who would do that?

for the record...it was 98 ambient in Montgomery TX this weekend. hwy cruise was at 173 degrees. S&G traffic was 185 degrees.

way back - I predicted I would top out at 185 on hwy. reality = 173

 

The whole TC aspect of the conversation also blows another gaping hole in the cold fluid causes condensation argument. Sure in the pan it may be 180, but the fluid still reaches well in excess of 200 in the TC rather frequently.

 

That's another question I asked and ipt responded, what condensation from where? I'm just repeating his reply.

 

Was this changed for 21? I don't see anything like this near my puck. Coolant enters and exits nipples attached to the puck.

 

I know some may have only the warming/cooling puck. I haven't seen if it's a tow pkg deal or certain areas.
@Ponderosa_Pine any insight?

 

Only trucks through 2018 can be pinned open. 2019-2021 don’t have a cooler or thermostat to pin.

Some of the early trucks won’t have a cooler if they didn’t come with the tow package. Most do.

 

Thanks. I was a little confused. Some one up thread with a 2020 in their profile was talking about pinning their thermostat.

 

They probably added a cooler. You can piece together a system using the older thermostat and adding a cooler and lines.

 

Or you can just straight line from trans to a air/oil cooler from the transmission. Saves some money...Mostly for warm/hot climates without cold winters. I did ok down to 30. Took 20-30 minutes to reach 150deg then stayed 170deg.

 

Personally I wouldn’t want my trans taking that long to warm up for short trips in the winter. I’ve got no issues pinning March-November here but winter months I’ll take the quick warmup since it isn’t unusual for me to have 4-5 short trips and no drives over 15 minutes.

 

True. And even the warming puck acts as a cooler if your TC is over engine coolant temp.

 

Yes my 2021 in stock form was not pinnable but added a trans cooler that is (after needing a transmission rebuild).

 

What happened that made you need a rebuild?

 

No no no no no...

 

Not entirely sure but some combination of 650ish crank hp + 35s + magnuson tune + stock transmission + no trans cooler equals losing 2-3 shift and reverse (same clutch as 2-3 shift). I would guess a stock NA engine and even an off the shelf 550hp magnuson install would never need a rebuild.

 

Ok a tad more data

I have a pinned trans cooler

in the winter I would cruise at 170

now in the 100 degree houston heat, I still cruise at 170

you would think the ambient rise would show up in my cruise temp

but noooooo.

 

Had some random thoughts reading through this:

If you pin the transmission thermostat, does the fluid in the heat exchanger drain back into the pan when the truck is off?

If fluid does drain back into the pan when the engine is off, what if your thermostat is un-pinned and you turn the engine off while the transmission is hot enough for the thermostat to be open. Fluid drains back into the pan and it is "overfilled" by the volume of fluid in the HX. Fluid cools and thermostat closes, then the transmission is running over capacity until you get the fluid hot enough to open the thermostat again next time you drive.

 

The thermostat can't close if it's pinned open

 

Right, my thought was if the thermostat is NOT pinned and you turn the engine off while the fluid is hot enough to open the thermostat - Does it drain back into the pan and overfill the transmission if everything cools off enough to close the thermostat?

 

You mean like every single day when you drive it and shut it off at night and let it sit all night with the thermostat functioning as Toyota designed it to do? You mean like that?

 

Its not running over filled, when you do the temp check for fluid level per the manual you need to pin the thermostat in order to get the correct level. Plus pinned or unpinned the fluid always drains into the pan it just wont pump to the cooler while it is unpinned and below temp.

 

Installed a trans cooler and saw temps hovering around 198-207 while towing. 200 was where it hovered.

TC spikes were up to 220 on hills. Tow/haul and D.

After leaving the thermostat pinned (thanks to this post) cruising without towing temps are staying at 170-175. Towing camper I’m not seeing anything over 200.

Will be leaving it pinned open going forward…

 

Blackstone report on my drain/fill right after the cooler install. This is with several trips towing our 7k lbs. travel trailer.

not bad.