trans temp

[puller]

I noticed when towing my trailer in stop go traffic and the outside temp was about 96 the transmission temp climbed to 220 and it took a good while to drop down to the normal towing temp about 160 to 175 range. The sensor is on the output line to the coolers I have added another cooler with a fan but it continues to run hot when in traffic. Everything is stock on this truck. Does any body have an answer to this problem?



Puller

 

[cerberusiam]

Its normal for it to do that in fluid coupling. A good TC will help keep those spikes down some but will eventually climb over 200 degrees under those conditions. If thats the highest temp your seeinf its fine, thats within ATF+4 operating range.

 

[puller]

Does anyone know what the highest temp is before bad things start to happen?





Puller

 

[cerberusiam]

Does anyone know what the highest temp is before bad things start to happen?





Puller

There is no real hard and fast temp for "bad" things to happen. The operating temp of the trans and fluid is pretty much defined as 140-260 degrees with the OE sensor throwing a fit at 260 degrees.



ATF+4 is rated 320 degrees for 1500 hours and still pass the defined ISO tests, doesn't mean the trans is going to handle it but the fluid is supposed to. If you want a limit to shoot at 240 degrees for an upper limit seems to be a safe number.



Now what does that number mean in relationship to location. Is it in the hot line or the pan? What is the time period that is dangerous for it to be at this temp in what location?



See what I mean, no rock solid place to put a hard stop.

 

[monkeyman]

I use Amsoil in my trans and it has never went over 185, runs cooler than normal ATF
Rick

 

[Yo Hoot]

I noticed when towing my trailer in stop go traffic and the outside temp was about 96 the transmission temp climbed to 220 and it took a good while to drop down to the normal towing temp about 160 to 175 range. The sensor is on the output line to the coolers I have added another cooler with a fan but it continues to run hot when in traffic. Everything is stock on this truck. Does any body have an answer to this problem?

Puller

That is my experience. Matter of fact 220 at the cooling line around town pulling a trailer is cool!

Monkeyman, maybe my next flush I'll go with Amsoil. Where are you taking your temperature from? If it's off the pan you aren't comparing apples. The pan will ALWAYS be at least 20 deg cooler than exiting the TC.

 

[rscurtis]

Measuring the temperature in the hot line is like trying to determine the temperature in your house by measuring the water temp. leaving the boiler. The pan gives a much more accurate indication of actual temperature.

 

[cerberusiam]

Measuring the temperature in the hot line is like trying to determine the temperature in your house by measuring the water temp. leaving the boiler. The pan gives a much more accurate indication of actual temperature.

Who cares what the temp in the boiler is, we want to know what the temp of the house is so we can adjust it.



Its not really a good analogy. With a transmission we want to know what the temps are doing so we can adjust driving style and shift up or down depending on the conditions. With 95% of the heat being generated in the TC thats what we want to watch. Reservoir temps will follow hot line temps.



The hot line gives us that reading when in fluid coupling so we don't over run the temps trying to let the trans do the thinking. They are really dumb and will cheerfully heat theselves up to the point they go into limp mode.



In lockup mode the hot line temp generally runs within 20 degrees of pan temp, less in some trucks. We see 260 degrees in the hot line pulling a hard grade in fluid coupling, downshift and lock the TC and now we can make sure we aren't over working the trans.



With the probe in the pan you have run 5-10 minutes at 260 plus degrees before you see enough of a rise to register. Will take twice as long to cool things off when you see there is a problem.



Hot line is much more useful, responsive, and accurate.