Descending Steep Downgrades In An Automatic

Today was a real rookie wake up call of day in my short solo run. I trained in a manual & was able to hold I-15 into Phoenix without any braking in a low gear. Today I’m descending a hill just after an exit called Dead Man’s Pass on I-84 west in Oregon. It’ starts right after a weigh station at an elevation of about 6600 ft. I knew it wasn’t gonna be good when I looked down and could actually see the “S” turns at different levels of the hill.

I turned off the cruise control. Downshifted into 7th & set the jake to medium. It started off fine but my rpms kept increasing around the 2000 mark. I tried downshifting again but the lower gears weren’t available. Meanwhile I have other trucks zipping past me & I can’t fathom why it’s not holding like in the manual.

The “wet my shorts” moment was when I was near the bottom & my right trailer axle was smoking as I tried to reign in my speed. I was letting her get to 35-40 & braking her back to 25-30. I must of did it too much at that point & having seen 2 trailers on fire after Mont Eagle, this really spooked me.

I immediately let off the brakes & let her coast to around 70. Dropped the jake which leveled her off & brought her back under control. I didn’t touch the brakes for 80 miles until I exited at the Love’s in Boardman.

The training video says that I’m supposed to set the jake then set the cruise to my desired speed. I was told to do this by a friend of Rainy’s (my trainer). Another driver said I should’ve been in a lower gear but my rpms would jump to over 2000 in anything below 7th.

Here’s my concern other than my heart rate after this episode. In bad weather (snow or rain) both the cruise control & jakes are not an option. How then am I supposed to keep a 68000 lbs rig under control with this auto trans?

We'll need some more information about your truck before we can really help you. what year and model do you have?

We'll need some more information about your truck before we can really help you. what year and model do you have?

An ‘18 Freightshaker lightweight.

I drove a 2018 Freightliner daycab for a year. The cruise control really had me spoiled. On hills you can depend on the "adaptive" cruise control to keep you below your maximum speed. The ACC will manage the Jakes to keep you from overspeeding.

Hint: Going downhill with the ACC, if you press on the brakes the cruise control naturally shuts off. But if you need just a touch of slowing down, bump the Jake switch to "high" for a moment. That'll do ya.

Well, I don't have an answer worth a damn for ya cause I'm still figuring out all this myself. But two days ago I probably spent about 20 miles or so on a 7% grade slapping that Jake on and off (and puckering a whole bunch) in an '18 Freightshaker.

My trainer believes brakes are mostly made for city driving, which means I'm rarely allowed to touch that pedal. So I can say with confidence that in a court of gravitational last resort, that jake can truly perform miracles!

Combine that Jake with the cruise, and you can do some pretty neat tricks to manage speed. Mind you, I'm still learning all of it. But I've seen enough to believe in it.

Now as for bad weather... Simple, I'm calling fracking Uber!

Splitter. I've traveled that and similar roads a bunch in the same vehicle. Forget manual shifting in good weather. Just put it in Jake 2 before your speed gets too high. When your speed is where you want it, brake 5mph down, release, and repeat. If your rpm gets too high, same thing.

When winter comes, use manual mode for downhills in bad weather. The lower speed you'll take will allow you to use 7th or 8th as needed to help control speed at maybe 25mph or whatever is needed for conditions.

Soon, I'm getting a 13speed trans...looking forward to that on those bad weather days and in parking. But you can handle it with the auto.

Today was a real rookie wake up call of day in my short solo run. I trained in a manual & was able to hold I-15 into Phoenix without any braking in a low gear. Today I’m descending a hill just after an exit called Dead Man’s Pass on I-84 west in Oregon. It’ starts right after a weigh station at an elevation of about 6600 ft. I knew it wasn’t gonna be good when I looked down and could actually see the “S” turns at different levels of the hill.

I turned off the cruise control. Downshifted into 7th & set the jake to medium. It started off fine but my rpms kept increasing around the 2000 mark. I tried downshifting again but the lower gears weren’t available. Meanwhile I have other trucks zipping past me & I can’t fathom why it’s not holding like in the manual.

The “wet my shorts” moment was when I was near the bottom & my right trailer axle was smoking as I tried to reign in my speed. I was letting her get to 35-40 & braking her back to 25-30. I must of did it too much at that point & having seen 2 trailers on fire after Mont Eagle, this really spooked me.

I immediately let off the brakes & let her coast to around 70. Dropped the jake which leveled her off & brought her back under control. I didn’t touch the brakes for 80 miles until I exited at the Love’s in Boardman.

The training video says that I’m supposed to set the jake then set the cruise to my desired speed. I was told to do this by a friend of Rainy’s (my trainer). Another driver said I should’ve been in a lower gear but my rpms would jump to over 2000 in anything below 7th.

Here’s my concern other than my heart rate after this episode. In bad weather (snow or rain) both the cruise control & jakes are not an option. How then am I supposed to keep a 68000 lbs rig under control with this auto trans?

I guess that cruise control is where it’s at for me. Set that puppy below my desired speed & use the jake accordingly or at the same time depending on the grade. I’ll tell ya, seeing those curves from the top of hill made me feel like I was on a roller coaster ride. But that was no fun at all. At least I didn’t have to use the escape lane.

I disengaged it & depended on the lower gear to keep me at or below 35mph. I even had the jake on medium. I would use the brakes to bring her back down when the rpms or my speed we’re picking up. It was usually both.

Thank you all for your input.

That is one thing I disliked at first, with the International LT, or at least, my LT. The ACC doesn't work for diddly squat with my Jakes. I really got spoiled on my mentor's truck, and then my first Freightliner Lightweight. Now, put it in 8th or 9th, set my Jakes, and then break as needed to maintain speed. Although, I sometimes forget to put it back in auto mode.

When I was driving a lightweight Freightliner with an automatic, I found that if I set the jake on stage 3 and the cruise 5-7 mph below the speed I wanted to maintain, worked great. Never had to touch the brakes going down the grade, the combination of the automatic & jake kept me at or below my desired speed all the way to the bottom. Yes, the rpm's shot up to about 2000, but the jake works best at about 1800 rpm.

Just something to think about.

Ernie

That's Cabbage Hill! There's a truck stop not far after that hill where you can get your "I survived Cabbage Hill" shirt lol.

The Autos hill decent is magical on that hill in dry weather. At the top of the hill engage the engine brake (position 1 is fine) and then set the cruise at the speed you want to decend the hill at. I set mine at 45 or lower. The computer will shift transmission and modulate the engine brake between setting 1-2-3 to hold your set speed. If you hit the foot brake it will cancel out the hill decent mode and you'll either have to reset it or go down the rest of the way manually.

Also I believe the lightweights have a smaller engine than the full-size, so your engine brake will have less torque. You may want to set it at a lower speed to compensate.

I only had to go down that hill once while it was wet and foggy. I just went very Very VERY slowly.

Anticipate snow or ice on that hill? F that I'll be at the rest area or one of the truck stops up the road waiting for conditions to improve.