How to Safely Descend a Mountain Grade With an Automated Manual Transmission

By Dan Drella Feb 9, 2017
Schneider tractor-trailer

Many truck drivers know that Schneider strives to give our drivers the latest technologies to ensure they have the best tools to do their jobs. But did you know we thoroughly test each and every technology in order to understand the safest, most effective ways to use it? Last year, we investigated the best ways to handle mountain descents in trucks with the new D-12 Automated Manual Transmission (AMT).

Schneider’s safety team partnered with Freightliner’s engineering team to test the automated transmission on the steep 6 percent grade of Oregon’s Emigrant Hill (or Cabbage Hill), selected based on a mountain grade driver survey. We installed heat sensors on the truck’s brakes to monitor brake temperatures in the 90-degree summer heat. We made 39 trips down the hill, testing different D-12 functions, to bring you these tips on performing a safe mountain descent:

Dry Weather Mountain Descents With Automated Transmission

  • Cruise control: Set your cruise control for 5 mph below the recommended descent speed. Cruise control will use the Jake brakes to maintain the set speed as the steepness of grade varies.
  • E-Coast: This mode conserves fuel, allowing the truck’s speed to increase until its speed reaches the cruise-set range, at which point it will apply the Jakes.
  • Descent mode: Descent mode in the Cascadia truck is similar to cruise control, except it will maintain speeds within 2 mph of your set-point and will not allow E-Coast to engage.
  • Downshifting in automated mode: Push the shift selector down to request a downshift. If speed and RPM allow, AMT will carry the downshift out. If not, you’ll need to use foundation or Jake brakes to slow the truck. This is similar to shifting in a manual transmission.
  • Snub braking: Allow RPMs to climb to 1,900, then apply brake pressure to reduce to 1,800 within five seconds. Let RPMs climb to 1,900 again and repeat.

Inclement Weather Mountain Descents With Automated Transmission

  • Remember not to use cruise control or Jake brakes during wet weather, as applying Jakes on a slippery surface can lead to wheel-lock.
  • Manual mode: Set a gear at the top of the grade, based on the speed you plan on descending. You must control speed using retarding force of the engine and foundation brakes to keep RPMs below 1,900 to avoid engine damage.
  • Light steady braking: In inclement weather, light steady braking is recommended. It uses less braking force but uses it more consistently, which helps avoid wheel lockup. Speed is important. During our tests, brakes began to overheat as speeds exceeded 20 mph.

With the D-12 Automated Manual Transmission, truck drivers have a number of tools to help you safely descend steep grades. Which tool you choose depends largely on the weather and road conditions. Check out other Slice of Orange safety blog posts for more truck driver tips on staying safe on the road. Schneider drivers can always talk to a Safety and Training Manager.

Have you driven the D-12 Automated Manual Transmission on a mountain grade? What has your experience been like?

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About the Author

Dan Drella IMG

Dan Drella is a Director on the Schneider safety team. Dan is accountable for safety for the Intermodal, Logistics Transportation and Logistics Transloading and Distribution areas. He has been with Schneider for 17 years working in various areas, including equipment management, rail management and finance.  

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