MOUNT VERNON, Wash. — Paccar’s new automated transmissions were put through testing and demonstrations during a daylong launch event at the company’s technical center here, as media were given the chance to experience the new units firsthand.
During a series of tests at the facility’s proving grounds, journalists did the driving while Paccar representatives rode along to provide guidance. They discussed how the 12-speed unit’s shift algorithms and computer controls are optimized for the best balance of fuel economy and performance.
Day cab and sleeper variants of the Kenworth T680 and Peterbilt Model 579 were tested, all of them equipped with the Paccar MX-13 diesel and the new transmission. Kenworth T680 day cab and sleeper models were driven by Transport Topics and others. In one series of tests, drivers were asked to launch the truck from a stop with the pedal depressed 25%, 50% and then all the way to the floor. Each time, the shift dynamics were largely identical. This, Kenworth General Manager Mike Dozier said, is the result of Paccar’s desire to develop a transmission that does the job while staying within an operating range that promotes longevity and fuel economy. “It is so good at gear changes,” he said. “The technology lends itself well to the continual progression of change intervals.”
INTRODUCTION: Paccar unveils new automated transmission
In another test, which also began from a standstill, drivers lifted off the brake and waited until the transmission’s “urge to move” feature kicked in. This feature, Paccar said, propels the truck forward when the brake pedal is lifted. Another feature, called “creep mode” is designed to help drivers navigate tight spaces by maintaining a slow pace without the accelerator being depressed.
In the test, once the brake was released the truck eased its way forward and a sharp right turn on the track was administered without use of the accelerator.
Based on road conditions that include grade angle, the engine also will select the optimal gear for take-off, the company said.
Joe Howard/Transport Topics
To help slow the truck, the transmission’s steering column-mounted gear selector also controls the engine brake. Clicking the stalk up and down allows the driver to select one of four engine brake settings. If one s selected, when the accelerator pedal is lifted the truck’s computer controls will sense that the driver intends to slow down, and engage the engine brake. The degree of deceleration varies based on the level selected. Two reverse gears determine the pace of backing maneuvers, and each also is controlled by the stalk. While reverse, neutral and drive modes are selected via a dial at the end of the stalk, the driver can switch between reverse gears by toggling the stalk.