Transmisson Operating Temp

cowboy21 · December 18, 2007

What is the best operating temp. for our transmissions? While pulling my enclosed trailer I noticed the temp got to 185 degrees in stop and go traffic. What is the hottest temp the tranny can run at without doing damage. I always pull in drive 3 and not in overdrive to keep the tranny in good health.

Thanks

Zembonez · December 18, 2007

What is the best operating temp. for our transmissions? While pulling my enclosed trailer I noticed the temp got to 185 degrees in stop and go traffic. What is the hottest temp the tranny can run at without doing damage. I always pull in drive 3 and not in overdrive to keep the tranny in good health.

Thanks

I've seen 200 once while pulling my boat on a hot day in the hills. Otherwise, 160 - 180 is pretty normal. Not sure what the danger zone is...

chris83 · December 18, 2007

The highest temp I have seen mine reach was just under 95.. That was in the summer while pulling my 18' open car hauler

Nytemare · December 18, 2007

your a Canadian too aren't you 2000silv2500.

95*F would be a super cool trans.

I would say somewhere in the same range as your thermostat is normal. Unless you have a tow package the trans is just cooled by the engine coolant.

chris83 · December 18, 2007

your a Canadian too aren't you 2000silv2500.

95*F would be a super cool trans.

I would say somewhere in the same range as your thermostat is normal. Unless you have a tow package the trans is just cooled by the engine coolant.

Yep I would be a canadian from delta, BC

todoubled05 · December 18, 2007

pulled my buddies duel jetski trailer yesterday from a distance of 20 miles hottest temp was 194..in the summer (texas) 200 trip avraged at 185 hauling nothing.around town 176 to 180

ChrisNJ · December 18, 2007

I don't remember exactly the numbers, but it was something like over 200 is the fluid doesn't like it, 210 starts breaking down a little, 220 starts breaking down a lot, 230 forget-about-it. But this may have been with the the old stuff, not sure if it was with the new dextron 6, and not even sure if the nbs' are getting dex 6 or not. my 06 allison 6sp had dex 6 and it was new new to it, couldn't even find it other than a dealer. and I think the dex 6 is some kind of synthetic, not sure if it's semi or full synthetic. hopefully someone can elaborate better than me.

My 6.2 6sp got to a high of 203 towing 8K this past summer with an average of 185.

luc · December 18, 2007

First,I'm not sure how accurate our tranny temp gauge are.

I know that on my 01 Yukon XL with the 8.1 engine, the water temp gauge read about 10* to 15* higher than the reading from my OBD2 scanner/tool.

That said, on my truck,towing a 24' enclosed trailer weighting about 11000#s at about 65mph,the average temp is about 170*/180* but can go as high than 215* when going up a very long and steep road in 100* + weather.

I believe than, on gas engines, the cooler used on the 3/4 ton is exactly the same than on the 1500 or Tahoe/yukon and a little bit on the small size.

I changed mine to a much bigger one but frankly, I have not seen a reduction in temperature.

I change my tranny fluid evey 30,000 miles and it always look and smell almost like new.

C & A s Dad · December 18, 2007

Cowboy, from all the research I have done on this, you are in good shape in the 180 range. Even 200 is not awful but if you are running 200 in flat lands or small hills, you will move up 20 or 30 degrees in the heat of the summer in some good hills or mountains. It is my understanding the trans temp warning light in our trucks does not come on until 250. This is too hot in my opinion. The new Dex VI is a full synthetic and it will certainly tolerate higher temps than conv. fluid. I still would not want to see 250.

luc, you are correct in saying the aux cooler used on 1500 and 2500 gas burners are the same. GM used this cooler as a good compromise. In my opinion it is too small for hot regions of the country like where I live but is likely just right for really colder regions. It is difficult to overcool a trans but in extreme cold climates a really large and efficient cooler could keep the fluid so cool it would never thin out and flow well.

If you changed your cooler to a much larger one and did not see any drop in temps, I am guessing you replaced the OE Stacked Plate cooler with a Tube and Fin style? A 5" x 11" x 3/4" OE stacked plate cooler will perform as well, if not better than an old style tube and fin cooler twice it's size. The stacked plate design is much more efficient and flows with less restriction. I have a 11" x 11" x 3/4" stacked plate cooler on my Yuk XL and on a 95+ degree day in moderate hills pulling a 6500lb camper, my highest temp has been approx 170 degrees. It typically runs low 160s when towing on a really hot day.

Check out what you have and you may want to replace it with a stacked plate cooler.

Nytemare · December 18, 2007

Cowboy, from all the research I have done on this, you are in good shape in the 180 range. Even 200 is not awful but if you are running 200 in flat lands or small hills, you will move up 20 or 30 degrees in the heat of the summer in some good hills or mountains. It is my understanding the trans temp warning light in our trucks does not come on until 250. This is too hot in my opinion. The new Dex VI is a full synthetic and it will certainly tolerate higher temps than conv. fluid. I still would not want to see 250.

luc, you are correct in saying the aux cooler used on 1500 and 2500 gas burners are the same. GM used this cooler as a good compromise. In my opinion it is too small for hot regions of the country like where I live but is likely just right for really colder regions. It is difficult to overcool a trans but in extreme cold climates a really large and efficient cooler could keep the fluid so cool it would never thin out and flow well.

If you changed your cooler to a much larger one and did not see any drop in temps, I am guessing you replaced the OE Stacked Plate cooler with a Tube and Fin style? A 5" x 11" x 3/4" OE stacked plate cooler will perform as well, if not better than an old style tube and fin cooler twice it's size. The stacked plate design is much more efficient and flows with less restriction. I have a 11" x 11" x 3/4" stacked plate cooler on my Yuk XL and on a 95+ degree day in moderate hills pulling a 6500lb camper, my highest temp has been approx 170 degrees. It typically runs low 160s when towing on a really hot day.

Check out what you have and you may want to replace it with a stacked plate cooler.

Would there be any way of strapping a fan to the stock cooler? That would help flow out a bit, and if its already a fairly efficient unit, would probably double its ability and cost way less than buying an aftermarket cooler.

C & A s Dad · December 18, 2007

I considered adding a cooler the size of what I have along with a thin line fan in front of it. Hayden now makes this as a unit but at the time I was doing it they did not.

I checked with my contact at Hayden and they suggested not doing this unless it was going to be mounted in a remote location with little to no airflow. He said if you did add a fan in front of the cooler you would limit the air flow when the fan was not running making it run even hotter. Of course when the fan was on it would be great but you would not want to run the fan all the time.

A good stacked plate cooler is not all that expensive and is a really easy swap.

luc · December 18, 2007

Trey:

no, I replaced mine with a Earl stacked plates sized 12X5X1.5 ( the factory one is 11X3.3/4X3/4)

I wanted to reuse the factory lines, so the the spacing between the ports dictated the size.

I tthink thay my "issue" is may be that the cooler is too thick to get good airflow through it.

C & A s Dad · December 18, 2007

luc,

You have hit the nail on the head. According to Hayden, they stopped offering the 1.5" thick models just for that reason. They are not as efficient and the same size cooler in a 3/4" thick model. Oil cooling is all about air to surface contact and the thicker models do not offer enough surface contact. GM used the 1.5" model until 99 when the 800 series trucks came out and then they moved to the 3/4" model.

Not sure where you are located in the country or your climate, but if you are in a hot climate with mild winters, I would suggest a 11" x 11" x 3/4" model. If you are in a colder area, step this back one notch.

Zembonez · December 18, 2007

The highest temp I have seen mine reach was just under 95.. That was in the summer while pulling my 18' open car hauler

I've never even SEEN a trans at 95 degrees (warmed up)... The air is normally hotter than that here in the summer. Is that some kind of Vulcan temperature reading?