GM Full Size SUV Transmissions Temps?

Well, just circling back with more findings.

I spoke with an independent transmission shop who told me that they could add another cooler, but that it likely would not make a huge difference. His statement was that with the Colorado elevations, that is what I should expect with a 1500.

The Yukon is at the dealer today for brakes, and I spoke with one of their technicians. He also said nothing to worry about. Said they checked the fluid and it is still good.

So, the moral of the story is tranny temps run hotter here and that is ok.

I am using my truck to tow my 5er and fishing boat over Monarch pass Friday. Somewhere around 16,000 pounds towed weight. I'll check to see what it's temps show, but I seem to remember that even getting to 220* last time.

So my results for temps are considerably different than some of the other claims on this forum.

bartlettj wrote:

parker.rowe wrote:
Highest I ever saw on mine is 200F, pulling a hill and the converter didn't want to stay locked in 3rd and I didn't feel like wringing it out in 2nd. Engine was at about 210F. ~6500lbs of camper and whatever was in the truck.

Mines older with the 4 speed 4l60E.

Normally runs about 185F, close to my engine coolant temp. I have the radiator cooler and the factory external cooler.

Some of the temperature readout locations vary. Coming out of the torque converter will be the hottest, after the coolers is the coolest.

I was reading the trans temp from the ecu in this case. Unfortunately I am not sure where the factory sensor is located in this truck.

I would not worry about 250 or even a bit more when working hard. As long as it stays cool on the flats the dealer is right... this is the new normal. Don't apply knowledge from the 1950s/1960s to today's fluid and transmissions.

BurbMan wrote:
250 is too hot, you don't want to be over 225.

I worked in automatic transmission design for one of the Detroit 3 about 30 years ago. 250F back then was starting to get a bit hot on those old "natural" oils, but certainly nothing that would hurt the transmission. With synthetic blends or pure synthetic, 250F is fine.

I found if I leave the AC on, I get to 220 on Monarch Pass. But leaving the AC off it's 20 degrees cooler.

parker.rowe wrote:
Highest I ever saw on mine is 200F, pulling a hill and the converter didn't want to stay locked in 3rd and I didn't feel like wringing it out in 2nd. Engine was at about 210F. ~6500lbs of camper and whatever was in the truck.

Mines older with the 4 speed 4l60E.

Normally runs about 185F, close to my engine coolant temp. I have the radiator cooler and the factory external cooler.

Some of the temperature readout locations vary. Coming out of the torque converter will be the hottest, after the coolers is the coolest.

I get up to 230 going over Monarch and Cotttonwood Passes but I always figured it was due to the lousy 3.08 gears I have in my truck. It always cools right back down though.

Lynnmor wrote:

Ralph Cramden wrote:
That was pulling a 5 mile long grade in excess of 15% in places here in PA with ambient above 85.

Wow, that would take you 700 feet above the highest mountain in PA, and that would be if you started at sea level.

LOL.....figures......... Is "in excess of 15% in places" that hard to comprehend?

Highest I ever saw on mine is 200F, pulling a hill and the converter didn't want to stay locked in 3rd and I didn't feel like wringing it out in 2nd. Engine was at about 210F. ~6500lbs of camper and whatever was in the truck.

Mines older with the 4 speed 4l60E.

Normally runs about 185F, close to my engine coolant temp. I have the radiator cooler and the factory external cooler.

I had the same engine and tranny in my denali. I saw 220-230 for quite a while pulling my TT. I hated it and thought it was too hot even though people said they are good until about 260 I think it was. I installed an extra trans cooler from e-trailer and never saw over 190 after that. It was super easy to install and if i remember right it was about $50 total. I really liked the peace of mind it gave me.