Transmission overtemp

[Elk101CH]

I have a 2008, 5.7L, six speed. I was towing about 6000 lbs, it was about -8 degrees out, going up hill, and my transmission temp gauge went from just below half to all the way into the red, and the transmission over temp light came on. I slowed way down, downshifted, and the temp dropped right back. I pulled over at the first chance and checked the transmission cooler, and it was very cold. Tow/haul was engaged. This happened one more time, then never repeated. The ride home was normal. Any suggestions on what could cause this?

[Jstowell2008]

could it have been iced over preventing any airflow to cool the trans fluid?

[tonyspin]

Any codes?

[Elk101CH]

No, the cooler was clear, and it did not have any codes

[SP]

I thought we has some sort of by pass that warms up the trans faster when its cold out.. If so maybe this is malfunctioning ?

[Elk101CH]

I will have to look into the transmission by pass fro heating the fluid. Thanks

[crzy2bealive]

subscribing!!!

[XFRONTIERMAN]

This transmissions have a thermostat,ever had a transmission service done maybe low fluid????.

[Elk101CH]

The transmission fluid level is good, and the condition is good. I did not know about the thermostat. Thanks

[oilmpg]

The same exact thing happened to me with my '10 5.7DC. About 18 degrees F pulling about 6000 lbs. up a long grade it 5th gear with tow mode on. The gauge went close to the red so I let off and soon discovered that 4th gear reduced the temp to normal. Using the cruise control caused lower gears to be used and the temp was normal when in use. It did it again a month later. I thought ice or snow may have blocked the cooler but it was clear. I never did figure out what caused this.

[Elk101CH]

Sounds like the same symptoms. If I find out what happened, I'll let you know.
Thanks

[Slate CrewMax]

From the pdf about the trans:

2. Transmission Oil Thermostat
The transmission oil thermostat consists of the poppet valve, bypass valve and element case (contains wax).
When the ATF temperature changes from low to high, the wax will expand to start to open the poppet valve
and close the bypass valve, thus switching the ATF passages.

maybe in extremely low temps the wax is not expanding soon enough.

[oilmpg]

Originally Posted by Slate CrewMax

From the pdf about the trans:

2. Transmission Oil Thermostat
The transmission oil thermostat consists of the poppet valve, bypass valve and element case (contains wax).
When the ATF temperature changes from low to high, the wax will expand to start to open the poppet valve
and close the bypass valve, thus switching the ATF passages.

maybe in extremely low temps the wax is not expanding soon enough.

This makes great sense. In warmer months I have no issues...it's only when it is well below freezing that the overheat has occured. My '08 Tundra transmission never overheated making the same winter trips. The second time the temps began to go up I experimented a bit. I could hold the temp at 3/4 on the gauge (1/2 being normal) just by modulating the accelerator in 5th gear. If I downshifted to 4th, the temp dropped back to normal. If I stayed in 5th and did not let off while going up a slight grade, I know I could make the red light come on...not a good thing to do.

The problem will be trying to get the dealer to take a look at it. I cannot duplicate the overheat in this weather. I thought about taking a video of the gauge while driving but never did it. I wonder if the Toyota tech would accept that in lieu of actually witnessing the transmission overheating.

[marlz]

Originally Posted by oilmpg

This makes great sense. In warmer months I have no issues...it's only when it is well below freezing that the overheat has occured. My '08 Tundra transmission never overheated making the same winter trips. The second time the temps began to go up I experimented a bit. I could hold the temp at 3/4 on the gauge (1/2 being normal) just by modulating the accelerator in 5th gear. If I downshifted to 4th, the temp dropped back to normal. If I stayed in 5th and did not let off while going up a slight grade, I know I could make the red light come on...not a good thing to do.

The problem will be trying to get the dealer to take a look at it. I cannot duplicate the overheat in this weather. I thought about taking a video of the gauge while driving but never did it. I wonder if the Toyota tech would accept that in lieu of actually witnessing the transmission overheating.

I would start a new thread since this discussion happened over a year ago but I am having a similar/same issue.

I won't be able to call the dealer to bring it in until after xmas so finding out exactly what happened won't be for a while. Did you ever find anything out from the dealer?

I have a 2011 rock warrior 10k miles. My friend and I traveled from Minnesota to Togwatee Wyoming for a snowmobile trip. I wasn't towing a lot. Just us 2, our gear, and a couple of ski doo 800 mountain sleds on an aluminum 2 place sled trailor.

16 hours one way. And on each trip about half way through, my transmission would over heat in 5th gear. Slowing down and letting it drop in to overdrive would solve the issue. Or kicking it down in to 4th would also lower the temp.

Each time it happened the situation seemed similar. The temp outside was 15 degrees or lower. And each time it happened the transmission seemed erratic. Holding 4th way to long and reluctant to drop in to overdrive.

We would take it easy and slow down for about 15 minutes when the tranny went in to H. After it resumed a normal temp we drove the rest of the way just like we had done before the experience.

I found this to be so odd. Why wouldn't it overheat at any other points on the trip? Why did the air temp have to be so low for this transmission problem to occur? How come I have only found 1 similar thread and no one else has had similar issues?

I have pulled larger loads in worse conditions with my tundra and have had no problems. Any ideas guys? I'll make sure I keep everyone posted on what the stealership has to say.

Hearing from my buddy about how his sierra denali pulls the trailor sooooo much better wasn't fun either.

[Big Shasta]

You could always lock the thermostat in the open position as described in this flushing procedure. Just as a temp fix if you were towing and it seemed like it wasn't opening.