Pinning open the transmission cooler ??

I have read all of the threads on transmission coolers and tranny temps and pinning open the cooler but I have not seen a comment on leaving the cooler pinned open

We will be towing through Neb, S. Dakota & Montana a 7000 travel trailer and given the time of year I want to keep my transmission as cool as possible. Here in Ks on a 95 degree day in the Flint Hills i was getting readings of 205 on my ScanGuage 2 while towing the trailer for an hour.

Since I will be towing for up to 8 hours a day in summer heat can I pin open the cooler at the start of my trip and leave it open until I drop the trailer in Mt?

Any input will be greatly appreciated..

 

I tow trailers with civil war cannons all re-enacting season, pin open in April, unpin in November. The only down side is that I have read that the transmission won't shift into OD until it reaches 140 degrees.

 

WELL &*&^^%&**,,, After posting I saw this thread I have not seen before. https://www.tundras.com/threads/transmission-fluid-temp-too-cold.32001/

I'm pinning it open at the start of the trip.

 

imo it's a waste of time, the thermostat is to get the fluid to heat up. If it's pinned open, once it gets hot enough that the thermostat would open anyways it's not going to make a difference. 205 is not high for these trucks. They run at 190-195 unloaded to begin with.

 

I hear what you're saying but my concern is the load, extended drive time and steep hills/ mountains.

 

According to my Scan Gauge I hit 240 a few times on my last trip. Was going over a couple passes in S4 and even S3 and had the Tow/Haul on. Hoping that pinning the cooler open will help. Going to Yellowstone next month, will have much bigger passes to climb than my last trip.

 

Temps (F) for reference:

Non-towing: Pan 180-225 and TC 180-240
Towing: Pan 180-235 and TC 180 to 250

Fluid flash point of 347 degrees and boiling point of 600 F.

 

Is running at 240-250 not a big deal? Would it be safer for me to pin the thermostat open? I’m buying a 3/4 ton diesel in about 6 months. I don’t want to spend money upgrading the cooling so I thought pinning it might be a good temporary solution.

 

Newer Tundras run hot. It’s part of the the design and the fluids are intended for it. The warning light only comes on at 300 F. Stay below that and you’re safe.

I see spikes towing over mountain passes around 245 but they are usually short lived and I’m not concerned.

Personally I see zero reason to pin - low temps aren’t good either.

 

We left Kansas and are in upper Montana now and I have been pinned the whole way. Average temp has been 170- 190 on the flat and the only time I had a high temp was east of Butte on 90 with a long 7% grade and I hit 242 in S4 and S 3.
99% of the trip the truck has pulled the 7700 lb. loaded trailer perfectly except for the on huge hill outside of Butte.
Wirth the ScanGuage II it has been interesting to watch the temps and what happens in different conditions and different gears. Yesterday we drove (No trailer) through a lot of hilly country with a lot of curves and in D the temp started to rise but immediately dropped when I dropped to 4 and 5.

Right now I am seriously considering an F 350 for the future for more pulling power and better stability. The tundra pulls good but it is also marginal. I love my Toyota's and I know I will be asking for problems with a non Toyota truck but I also like being safe. I'll probably wait until Toyota introduces the new model and se what the specs are but I am not very hopeful.

 

I've been on that hill outside Butte, it's a long one.

 

Toyota's WS Semi Synthetic fluid is very mediocre, Its produced by mobil for toyota and meets minimum requirements . If someone is seeing 245 degrees they should really upgrade to a high quality full synthetic fluid . ( amsoil signature series )
Its not that these transmissions were designed to run hot , its the manufactures purposely making them run hot to achieve optimal fuel economy to satisfy government CAFE requirements . Its the same story as why toyota suggests to use 0w20 motor oil over 5w30 . The engine was not specifically engineered to use 0w20, theres been No bearing or clearance changes since 2007 when the 5.7 was introduced . Its just to satisfy government regulations . thats it .but thats for another thread .... I digress .

My argument is that there is nothing wrong with pinning the thermostat open when going on long Multiple Hour towing trips in the summer heat . The trans will warm up quick regardless due to fluid still flowing through the warmer and the added load the transmission is put under towing the trailer . I haven't seen anyone report actual temp numbers with pinned thermostats towing . My prediction is that pan temps will be somewhere between 180 and 195 .
Thats not "over cooling" , nor going to hurt the trans in anyway .

 

Just to add that the 11-18 Tundras don't have much in the way of coolers to start with.

 

This is true , using the upper few inches of the a/c condenser inst the greatest cooler .
My 2015 sierra was like that too ... didnt cool that well either