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Cummins_2013_ISX15_FrontGear Down Protection Explained

Cummins paved the way in developing electronic features aimed at assisting drivers and protecting equipment. In fact, we are developing more features to enable efficiency gains while still completing on-time delivery. Load Based Speed Control (LBSC) and Gear Down Protection (GDP) are two of those foundation technologies, and they have become even more important with “downspeeding” and the growing number of less-experienced drivers.

It is important that your customers understand the difference between these two electronic engine features. Helping customers understand how the features work and interact will go a long way toward ensuring driver satisfaction while reducing fuel use and operating costs.

Cruising in the upper gear range provides steadier operation and enables the driver to achieve better fuel economy. GDP encourages drivers to shift into upper gear and avoid cruising one gear down (ninth gear for a 10-speed transmission) at high rpm, where the engine is not most efficient.

GDP uses a vehicle speed threshold with two settings that encourage drivers to shift into upper gear. Once the GDP light (lower vehicle speed) setting is surpassed, the driver is expected to shift into top gear. However, if the driver holds gear to increase the vehicle speed in gear down, and the GDP heavy (higher vehicle speed) setting is surpassed, the driver will be forced to coast down to the light GDP vehicle speed. The driver can shift into top gear to achieve the target road speed. When the vehicle is under heavy loads, the driver will be allowed to hold gear down up to the GDP heavy setting. This provides additional power to overcome road loads, avoiding further downshift.

The combination of LBSC and GDP, coupled with a lower Road Speed Governor (RSG) setting, can deliver a 3 percent to 5 percent fuel-economy boost in line-haul operations. A key factor for anyone setting up the engine operating parameters is knowing how to set the upper and lower mph limits on GDP (GDP heavy and GDP light) so that they sync with the engine rpm in the highest gear controlled by LBSC. These parameters are set using the PowerSpec tool – through the function that automatically calculates the proper numbers based on the transmission gear ratios, tire size, desired road speed and other factors, such as duty cycle.

GDP is designed to operate on vehicles equipped with manual transmissions, but it also functions when a driver takes manual control of a manual automated transmission.

Helping customers understand how these features interact will go a long way toward ensuring driver satisfaction while lowering fuel use and operating costs. For additional details about spec’ing an engine to meet customers’ needs for their desired combination of performance and fuel economy, visit

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