light vs heavy trailer temperatures

[NCMODELA]

Hi all. I wanted to start a discussion on something I saw with my 2003 yukon xl 1500. I tow about 6300 lbs loaded ( scale veified). Went to western nc when it was about 89 to 91of outside. Saw trans temps as high as 206 on large hills and around 196 running down I40 no grades. Engine temps around 206 as high as 215 or so.

I had to go pick up a single axle enclosed trailer for a friend. Could have weighed more than 2500lbs. Running it home down I40 with 95 to 91of outside I saw 194 to 198oc. Trans temps can't remember the engine.

Now the discussion. Obviously I'm towing max with one and the other should be nothing. But I am reading the same temps per the scangauge. I also notice I get the same fuel mileage towing the two. Is this all because of frontal area drag? I was afraid I was going to taxing my motor towing that heavy but if it reacts the same way temp wise between the two, is it all that bad?

Does anyone with a 2500 or excursion see a difference between the two trailers like that.

I will say though I do notice the larger trailer back there and I am slower to get to speed and slower up hills. Which was expected.

The only thing I haven't done is run the small one up a 7% grade vs the large one.

Thanks Bill

[bfourman]

blt2ski wrote:

bfourman wrote:
Temps will be pretty much the same with a 2500 series Suburban/Yukon, but the 4L80E is built to better withstand tough towing conditions than the 4L60E. Plus with a 2500 you gain the benefit of a stronger frame, heavier axles, bigger brakes and usually a deeper gear ratio.

You had it correct until you hit the gear ratio. The 4l60 actually has a lower first gear, so that trans with a 3.42 actually has a lower overall first gear ratio than a 4l80 with 4.10s. 3.1 vs 2.48 in the trans. A place a lot of folks do not compare the ratio's when they should.

Marty

Ok, so a deeper axle ratio. That doesn't change the fact that a 4L80 is a better trans for towing than the 4L60.

[blt2ski]

bfourman wrote:
Temps will be pretty much the same with a 2500 series Suburban/Yukon, but the 4L80E is built to better withstand tough towing conditions than the 4L60E. Plus with a 2500 you gain the benefit of a stronger frame, heavier axles, bigger brakes and usually a deeper gear ratio.

You had it correct until you hit the gear ratio. The 4l60 actually has a lower first gear, so that trans with a 3.42 actually has a lower overall first gear ratio than a 4l80 with 4.10s. 3.1 vs 2.48 in the trans. A place a lot of folks do not compare the ratio's when they should.

Marty

[bfourman]

Temps will be pretty much the same with a 2500 series Suburban/Yukon, but the 4L80E is built to better withstand tough towing conditions than the 4L60E. Plus with a 2500 you gain the benefit of a stronger frame, heavier axles, bigger brakes and usually a deeper gear ratio.

[whjco]

TomHaycraft wrote:
How does the "lighter" trailer compare to the "heavier" trailer in frontal surface area? Even if a negligible difference, I'll bet wind resistance accounts more for the fuel economy, than weight.

About 6 years ago I towed my 24' enclosed car trailer from KY to MN to pick up a '55 Chevy wagon using my 2000 Excursion 7.3. The terrain for the entire trip was rolling with no mountains and I got the same mileage going both directions so overcoming wind resistance seems to be the primary user of fuel. However, I would have anticipated my fuel consumption to be higher loaded than unloaded in the mountains.

[Tystevens]

MitchF150 wrote:
My 13 F150 will run 195* trans temps not towing anything in the dead of winter...

It'll run 195* towing my #5000 TT in 90* weather on the flats and rise to 210* on the grades.

I'll see 201* temps running empty going up grades at slower mph..

The key here is that my trans has a 'thermostat' set at around 190* and my trans temp is taken from the ECU, so that's why I get those temps in winter or summer, empty or towing.

FWIW, the trans temp numbers for my '11 F150 EB are virtually identical under similar situations. 190-195* unloaded (provided I've driven far enough for it to heat up), 195-200* towing flat ground, up to 215* towing in the mountains, and up to 205* unloaded going slowing up the canyon or something like that.

[Tystevens]

I have periodically towed an 8 x 15 gear trailer loaded w/ our scout troop's camping stuff. Weight is probably about half what my TT weighs loaded to camp. Frontal area is probably 3/4 of the frontal area of my TT.

When towing the scout trailer, most of my numbers are about the same as when towing my TT. Except for mpg, which is maybe 2 mpg higher.

[blt2ski]

Probably frontal area related more than weight. Generally speaking, for ea 2-3 sq ft of frontal area added to a base, the same HP is needed to keep you going 60 mph as 1000 lbs of actual weight.

For example, 15K lbs and 90 sq ft of frontal area, takes the same 135hp as it does to move 25K lbs with 70 sq ft of frontal area. 15K with 70 ft of FA, is around 105HP.

Hence why back in 92 when I bought a TT, at the dealership was a poster from ford. For full size pickups at the time, max trailer wt was 10K lbs, IF you had less than 80 ft of FA. 81-100 was limited to 7500 lbs, 101-120 was limited to 5000 lbs, trailers over 120sqft were not recommended you tow with your full size F series. The Ranger and Aerostars had something similar, but iirc it was a 6000 lbs max with 60 sqft, 61-70 was reduced to 4500 or so, 71-80 was down to 3000, over 80 sq ft was not recommended you pull with your v6 powered rig.

This is something the new SAE J2087 specs should include in the max towing numbers, but there is no such reduction. Same with the maximum grade you can start in 1st or reverse gear at 12%, if you know you will be towing up 15-20% grades, what is the weight reduction. If you try to start on a grade greater than 12%, it is possible you will not go forward!

Marty

[NCMODELA]

I guess what is interesting to me is that these and other people's numbers are possibly frontal drag and wheel/brake drag related and not actually weight related.

The only thing different was the coolant towing the to was 10* hotter than the box trailer.

[Trail-Mate]

The heavy trailer will cause the the Torque Converter to unlock more and this will raise the Trans temps and engine temps. Larger Trans Cooler would help and Synthetic Fluid would give you some more insurance. Not sure on a 2003 if you can get a tuner to manually lock the trans in 3rd gear. Transmission Torque Converter running unlocked will raise temps pretty quick. Pulling hills is where the GM trans usually unlock creating heat.

[MitchF150]

My 13 F150 will run 195* trans temps not towing anything in the dead of winter...

It'll run 195* towing my #5000 TT in 90* weather on the flats and rise to 210* on the grades.

I'll see 201* temps running empty going up grades at slower mph..

The key here is that my trans has a 'thermostat' set at around 190* and my trans temp is taken from the ECU, so that's why I get those temps in winter or summer, empty or towing.

My specific trans is designed to run at those temps, so I had a learning curve to adjust to from my old 97 F150 trans temps..

You are doing fine and your computer will tell you when the trans temps are too high and that's when you need to pull over and cool down and then re-evaluate your situation.

Good luck!

Mitch

[Campfire_Time]

This is normal. I recently towed a loaded 6x12 UHaul trailer over 200 miles. Mileage was only marginally better than towing my 4500# hybrid trailer and trans temps were about the same, around 190-200.

So long as the trans isn't running at 230 or higher for long periods it'll be fine. Make sure to use Dex VI instead of the speced Dex III. It's a synthetic blend that runs cooler than Dex III. Dex VI was introduced in 2006, and GM recommends using it in all older Dex III applications. If you have your fluid changed at a dealer they will not even use Dex III.

[NCMODELA]

No running about the same speeds. Right around 65

[nevadanick]

Were you gong faster with the enclosed trlr ? I can see temps higher without a trlr at high speeds than towing at low speeds.

[NCMODELA]

Same route 5 to 6 degrees hotter with smaller trailer. It is a enclosed box trailer.

Yes it is not exactly comparable but it is close. Close enough to warrant the question.

I see statements all the time. 1/2 ton suburban towing at gcwr. Your going to blow up the trans, overheat the motor, over heat the trans etc. There was 4000 lbs difference between those two trailers.

I would like to go to a 2500 sub or excursion but will I see the same thing with temperatures.

Fwiw. My 18 ft car hauler flat trailer brings my fuel mileage down to 13 hwy vs 18 hwy unloaded