PEC017
5/3/2018 Page 68 of 105
last gear that the second step of PGS will be active. While PGS is active, engine
speed will be “soft” limited to PGS First Engine Speed Limit (PS27) or PGS Second
Engine Speed Limit (PS29) depending on the currently selected gear and the
defined gear ranges for each step.
Gear Down Protection (GDP)
The Gear Down Protection module encourages the driver to shift into top gear when
operating the vehicle at the target operating speed. This is done by restricting the
road speed in gears below top gear. When enabled, GDP restricts operation of the
vehicle at the target operating speed when not in top gear. This effectively prevents
engine operation at excessive RPMs and, as a result, helps to improve fuel
economy. GDP is a “hard” limit. The engine RPM, and therefore vehicle speed, will
be limited to a specified value in the specified gears. Along with limiting engine RPM
and vehicle speed, this function also provides a visual notification to the driver to shift
via the driver display.
The gear down protection module offers a single programmable engine speed limit.
Selection of the GDP module will automatically set the engine speed limit at one or
two gears below top gear depending upon the combination of transmission, rear axle
ratio, and equipped tires. Changes to the factory settings can be made post-delivery
via a PRS file from the PACCAR Engine Support Center.
GDP First Gear Active (GP11) specifies the first selected gear in which the GDP
“hard” engine speed limiter will become active, while GDP Last Gear Active (GP13)
specifies the last selected gear that the GDP engine speed limiter will remain active.
GDP Active Gear Count (GP14) is the number of gears that GDP will restrict engine
speed to a maximum of GDP Engine Speed (GP12).
Application Guidelines
The SCM features are intended to be used with manual and automated-manual
transmissions while operating in manual mode. The SCM feature is not available with
2-speed rear axles, auxiliary transmissions, Allison transmissions, or multi-speed
transfer cases. A full list of application guidelines includes:
Transmissions
o Available on chassis equipped with Eaton 9, 10, 11, 13, or 18-speed
manual transmissions
o Available on chassis equipped with Eaton Ultrashift automated-
manual transmissions (while operating in manual mode)
o Not available on chassis equipped with Allison transmissions
o Not available on chassis with auxiliary transmissions
Rear Axle Ratio
o Available on chassis with 2.53 to 4.33 rear axle ratios
o Not available on chassis equipped with multi-speed rear axles
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