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08-08-2022, 12:00 PM
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#21
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Rivet Master
2024 23' International
South of Austin
, Texas
Join Date: Jun 2018
Posts: 675
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Quote:
Originally Posted by PatSoozy
Good morning,
Questions first (BLUF)-The transmission gauge on our truck reports as a graph, not with numbers. Many have said they watch the transmission temperature to not exceed “x” degrees. Any thoughts on how far past 50% on the gauge is danger zone and I should pull over and let it cool down?
Second question, using an IR thermometer to check brake temperature on a down hill run, some have reported 200 degrees as “not to worry.” Any opinions on what is the “to worry” temperature?
Background, We are long time flatlanders heading for Utah via Colorado with a 2020 F150 SCREW 3.5 SB Max Tow, pulling a 2021 25GT FBT and not a lot of water, maybe 6600#.
Thanks in advance.
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Your Truck gauge might have a setting to show you the actual digits, vs the graph. I wouldn't like that. You can get an OBD2 port plug and turn it on and drive down the road. Your phone app will give you precise temp readings. Mine is normally 200-205 even when towing in the mountains. But my camper is 4500LB. My screen though, shows the actual digits, not a graph.
" stopping ' is not always a good idea unless you are still pulling a hill and it is overheating. Keep going keeps fluids flowing at higher rate past the front radiator cooling fins and more airflow if its simply running on the 'warm' side of the range.
You shouldn't have any problems with brakes unless they are factory. I changed mine to a drilled/slotted heavy duty brand a couple of years ago so theres no fade.
If you control your descent with manual gear shifting, it should be fine. Your camper is not -that- heavy. Instead of riding the brakes on any vehicle, drop a gear with the manual switch and let the motor brake and dont be in a hurry going down-hill. Don't ride it. Use moderate braking to keep your speed consistent but dont ride that pedal for more than a few seconds to drop a few MPHs. That'll keep rotors moving, cooling and you'll be fine.
I've descended plenty of big mountain passes in CO WY NM UT MT with it simply in 4 or 5th grear and rarely touched the brake pedal but on some 20mph corners.
If your engine is racing going down-hill, you are going too fast. It should never really be in the 4500+ range. I rarely hit 3000 rpm except on some very very steep short mountain roads. But most aren't like this.
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08-08-2022, 06:25 PM
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#22
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Rivet Master
2007 27' International CCD FB
San Diego
, California
Join Date: Sep 2014
Posts: 2,119
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Quote:
Originally Posted by JJTX
If your engine is racing going down-hill, you are going too fast. It should never really be in the 4500+ range. I rarely hit 3000 rpm except on some very very steep short mountain roads. But most aren't like this.
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I would hesitate with this advice to limit engine speed for engine braking. That's like saying only ever use 50% of your brakes. Potentially leading to compromised safety situations when towing big loads. If not relying on engine braking, the next resort is to use more brakes. Which leads to real dangers on extended grades. It may also be why some may feel their vehicles don't provide enough engine braking.
You may not have experienced this towing 4500lbs. With larger trailers, it's a different ballgame and one needs to know how to use the broader capacity of their rigs braking capability to stay safe, and reserve caliper braking for emergency stops.
Engine RPM is not a function of speed, rather the degree of engine braking applied. Just like climbing, sometimes one may be in very low gears but very high engine speeds just to keep the load moving even slowly. Say 25 mph in extreme 8% grades at 8k feet elevation for example, where the air is thin and engine compression braking is further compromised.
With a large enough load, on extreme grades, physics takes over and the load will do what loads do when pointed downhill. It's sometimes very much necessary to use lower gears and higher RPM otherwise it becomes a accelerating freight train that brakes alone will not manage. It's rig and situationally dependent, but do not be afraid to use 2nd gear if the situation calls for it. Or sometime it's necessary to slow down the rig even further to grab 1st letting the engine speed run 5k+ rpm at 20mph, to manage momentum and downhill acceleration.
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08-09-2022, 06:22 AM
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#23
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Rivet Master
2024 23' International
South of Austin
, Texas
Join Date: Jun 2018
Posts: 675
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Quote:
Originally Posted by pteck
I would hesitate with this advice to limit engine speed for engine braking. That's like saying only ever use 50% of your brakes. Potentially leading to compromised safety situations when towing big loads. If not relying on engine braking, the next resort is to use more brakes. Which leads to real dangers on extended grades. It may also be why some may feel their vehicles don't provide enough engine braking.
You may not have experienced this towing 4500lbs. With larger trailers, it's a different ballgame and one needs to know how to use the broader capacity of their rigs braking capability to stay safe, and reserve caliper braking for emergency stops.
Engine RPM is not a function of speed, rather the degree of engine braking applied. Just like climbing, sometimes one may be in very low gears but very high engine speeds just to keep the load moving even slowly. Say 25 mph in extreme 8% grades at 8k feet elevation for example, where the air is thin and engine compression braking is further compromised.
With a large enough load, on extreme grades, physics takes over and the load will do what loads do when pointed downhill. It's sometimes very much necessary to use lower gears and higher RPM otherwise it becomes a accelerating freight train that brakes alone will not manage. It's rig and situationally dependent, but do not be afraid to use 2nd gear if the situation calls for it. Or sometime it's necessary to slow down the rig even further to grab 1st letting the engine speed run 5k+ rpm at 20mph, to manage momentum and downhill acceleration.
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I've towed 100,000+ LB loads. The theory is not much different.
If you need engine-braking in first gear, you are over loading your tow vehicle and probably need a brake/rotor upgrade in the light-vehicle towing realm.
5K gas engine braking should never happen at 20mph if you aren't over loaded, going too fast and arent experiencing brake fade due to inadequate tow vehicle configuration and brake capabilities.
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08-09-2022, 01:51 PM
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#24
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Rivet Master
2007 27' International CCD FB
San Diego
, California
Join Date: Sep 2014
Posts: 2,119
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Quote:
Originally Posted by JJTX
I've towed 100,000+ LB loads. The theory is not much different.
If you need engine-braking in first gear, you are over loading your tow vehicle and probably need a brake/rotor upgrade in the light-vehicle towing realm.
5K gas engine braking should never happen at 20mph if you aren't over loaded, going too fast and arent experiencing brake fade due to inadequate tow vehicle configuration and brake capabilities.
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And I invite you to come tow in some more interesting locations. Towing in the flatlands of Texas is a different ballgame to towing loads in more extreme grades at higher elevation. Thinner air at 8k or 10k elevation, greatly effects power, but also engine braking in all forms.
We may be talking past each other, and it'll depend on the rig. Diesels may use less RPM to similar effect. A blanket statement limiting to 3000rpm, especially for gasser, is a disservice and will get people in trouble when visiting the Sierras or Rockies.
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08-11-2022, 04:10 AM
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#25
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Rivet Master
2024 23' International
South of Austin
, Texas
Join Date: Jun 2018
Posts: 675
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Quote:
Originally Posted by pteck
And I invite you to come tow in some more interesting locations. Towing in the flatlands of Texas is a different ballgame to towing loads in more extreme grades at higher elevation. Thinner air at 8k or 10k elevation, greatly effects power, but also engine braking in all forms.
We may be talking past each other, and it'll depend on the rig. Diesels may use less RPM to similar effect. A blanket statement limiting to 3000rpm, especially for gasser, is a disservice and will get people in trouble when visiting the Sierras or Rockies.
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I tow in the rocky mountains every other year. Its not anything new.
I just don't believe revving a gas engine excessively is appropriate Or needed and usually means your going too fast.
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08-11-2022, 08:42 PM
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#26
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Rivet Master
2007 27' International CCD FB
San Diego
, California
Join Date: Sep 2014
Posts: 2,119
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Quote:
Originally Posted by JJTX
I tow in the rocky mountains every other year. Its not anything new.
I just don't believe revving a gas engine excessively is appropriate Or needed and usually means your going too fast.
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If you watch this video that highlights 3 of the most popular 1/2-ton gas trucks: F150, GM 1500, and Ram 1500 on a test of the Ike Gauntlet towing 9100lbs. All trucks are applying automatic grade logic and hold engine speeds 4000RPM into 5000RPM on the downhill section.
Yet in this test by professionals, all 3 trucks are criticized for automatic grade logic that is not programmed aggressive enough, requiring too much physical brake application. Suggesting that in manual control, they would opt to manually downshift further. Because the trade of more physical brake applications risks overheating pads in this type of situation.
Ike Gauntlet in the downhill only varies from 5% to 6% grades. There's routes easily steeper than this.
Not saying that one should be using over 3000rpm all the time. Just like brakes, we're not applying full brake applications regularly. When the situation calls, there's no artificial ceiling and the full spectrum of control to manage downhill momentum should be used and practiced.
To the point of this thread, it's better to use more engine braking than caliper brakes, as engine braking can't overheat.
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08-11-2022, 10:43 PM
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#27
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Rivet Master
1978 31' Excella 500
Genoa
, Nevada
Join Date: Jul 2007
Posts: 1,554
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If you see "Brake Check Area", "Truck run out roads", and big burn marks in the asphalt, and truck tires smoking or a blazing, that's a hint that you're on a steeper hill. Don't be that guy that's needing the runout road. Brakes heat up, light the semi trailer, the trailer burns into the asphalt and the road is shut down both ways for hours. Most annoying. Hear it on the radio very frequently going down I-80 into Sacramento from Reno. A lot of the kid drivers haven't been learned up on driving on the steep. Interesting road, Cal-Trans has signs up for "let it ride" when there's a hill coming up. And lots of signs to down shift, and brake check areas. Some nasty narrow 4 lane with the divider ON the white line, with trucks cruising down full speed. Lots of times Best to just fall back and watch the train wreck instead of trying to get in front of it by Auburn. Traffic will be going at snails pace in a few miles anyway.
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