Driving Mountain Grades With An Auto Trans

Topic 31800 | Page 1

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Matthew P.'s Comment
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The topic says it all. Tomorrow I will be facing some pretty steep grades. I would enjoy hearing from The experience drivers about how to deal with that.

Very unsure right now about how automatics handle on the steeper grades.

Hauling some machinery to one of the mines in Northern Nevada. Right now I am east of Kansas City. Shouldn't see too much today.

Once again I'd appreciate hearing a little bit of advice. I am driving a 3-year-old peterbilt.

JakeBreak's Comment
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Autos aren't too bad in the mountains. If you are running your Jake's then it won't upshift until you apply pedal again. You will want to learn where your optimal shift points for maintaining speed on a grade vs the economy shift points most companies use. And most importantly learn how to lock it in manual mode.

Matthew P.'s Comment
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I can pin it in 10th if need be and use the Jake's. Any other suggestions?

Autos aren't too bad in the mountains. If you are running your Jake's then it won't upshift until you apply pedal again. You will want to learn where your optimal shift points for maintaining speed on a grade vs the economy shift points most companies use. And most importantly learn how to lock it in manual mode.

Truckin Along With Kearse's Comment
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It depends on the truck. My Cascadia has "descent assist" or some such feature. Turn off cruise and Jake's. Then set the cruise to the speed you want and set Jake then coast down. I don't always use this feature. Most of the time I drive it like a manual.

My international didn't have this and the Jake's would not activate until you hit the brake.

So basically, I get to the speed I want, downshift it as necessary, then once I am at optimal speed with correct Jake setting let it ride. The 2nd Jake usually holds it and if not, 3rd will slow it down. I keep the Roma between 16 to 20rpm

Either way it isn't hard.

If you can't use cruise or Jake's due to weather. Use traditional stabbing brake technique

Stevo Reno's Comment
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All 3 Cascadias I drove, 2x 2019'sand a 2022 last the companies had manual modes off, so I couldn't drive like a stick. Cruise had the +5 mph, so depending on the grade, 3%, 6%, I'd set cruise at 5-7mph under posted speed, and let the trans do it's work. Sometimes, jake 1-2 if needed, off and on, using my brakes as less as possible (good weather not wet) And I used the steering wheel controls as needed to adjust my speed up or down.

Mostly once out of Calif lol where speeds are 70-75 I usually was under that, but if the truck started to go a couple mph over, then I'd brake, or jake whichever was needed to remain legal, ain't gettin' a speeding ticket! I liked the auto's, except when backing sometimes at weird docks, how trans can jerk around in reverse, when backing uphill angles at docks.

Like the hills coming into Albuquerque, NM I-40, the I-17 mountains from I-10 to I-40, etc, I rarely had to use the brakes, unless traffic flow deemed it neccessary.....I-15 Cajon Pass by my house, same, I'd set cruise at 40 since speed for trucks is 45 downhill.

PackRat's Comment
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I would use normal braking as needed, not "stab braking" unless it's an emergency. I'm not sure what that suggestion is about.

Just go below the speed limit on descent, using lower gears, and the engine brake settings as needed. Don't let it gain more than 5 mph more than you actually want. If it does, use the pedal to apply the brakes normally to 5 mph less than you want, all the while using the engine braking. Slow is safe. If you experience any brake fade, slow down.

If you can get to the bottom of the grade safely and without touching the brake pedal, you did it perfectly. Nobody wins reaching the bottom of the downgrade first.

NaeNaeInNC's Comment
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The 2019 Pete that my trainer had, he taught me to set the cruise 5 under my optimal speed, set the Jake to the first position, and see if it held my speed. If not, controlled braking until another 5 below where I wanted to be. Set again, and adjust as needed. The thing with automatics, in perfect weather, let the truck do it's job on the way down.

Davy A.'s Comment
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It really depends on how your company has trucks programmed. Ours coast to neutral on any downgrade, weather on the pedal or cruise. Any level of jake will negate that.

On all grades, I set my speed and gear before I go down the hill, set my jake at a level that is appropriate for the load. I usually will start out with a higher level than I need and go down from 3 to 2. Ill modulate jake levels to keep it within 5 mph of my target speed, and lastly use service breaks to do it if needed. Most hills I never touch my service brakes on. I rarely use more than level 2 of my jake. This is assuming your garden variety 5 to 6 % grade pass. I just did cabbage westbound today, 21k pounds in the box, 37 to 45 mph as recommended by the signs. Level 2 and occasional level 3 jake. Didnt use the service brakes at all. I just putt down it and take in the glorious views.

Some hills, ill set it into manual mode and then use the pedal to gain a bit of speed, if I leave it in auto, once the jake is released, it will shift to 12th and then neutral and pick up too much speed. These are hills like 89 in Utah going from Bear lake to Logan. Its a lot of varied hill/flat with tight turns, so I cant just set it and forget it. Ill manually shift as needed usually between 8th to 10th depending while just leaving the jake on. Ive done that hill several times loaded to 44k in the box. Ive found on that one that I need to use service brakes here and there, but I never just ride them down hill like I see others do.

My trainer told me "you can go down any hill too slowly as much as you want, you can only go down it too fast once."

David W.'s Comment
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If the weather is good it really doesn’t matter if it’s a auto or manual. If it’s bad weather and you don’t have manual mode, you just have to know at what rpm does the trans shift up, and keep it below that till you can shift and gain speed

Grumpy Old Man's Comment
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My 2021 cascadia is set for +3 on cruise. Set the cruise, go down hill. Truck will not let it go more than 3 over the setting. Automatically applies hakes, and I believe actual brakes as needed. Definitely will downshift as needed. You cannot go any faster, even if you hold the pedal to the floor. The truck will ignore the pedal and do it’s thing. My old truck (2017) would go faster and faster with the pedal down, but would also send an over speed report to the company.

To be fair the steepest I’ve gone down is 6% for 6 miles, and you can go 65 the whole way. Once I was really heavy and got up to 70. I just set the cruise to 63 and it kept it at 66-68 the rest of the way.

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