[3] Sharing design commonality with the Class 8 W900, the T600 differs from its counterpart largely with its set-back front axle, hood, and lower bodywork (with the Aerocab later adopted by the W900L).

The Kenworth T600 began life as a response to the 1973 oil crisis (which affected diesel prices in a similar manner as gasoline).

[1] Due to length restriction laws, truck development originally began on a cabover tractor (similar to a Kenworth K100).

To enhance the exterior design of the T600, Kenworth/PACCAR engineers experimented with scale models in the wind tunnel of the University of Washington.

[5] During testing of prototypes at the PACCAR Technical Center, the design of T600 was found to be over 20% more fuel efficient than a W900 with a comparable powertrain.

[5][6] At highway speeds with an identical payload as a standard-body conventional, the lower drag of a T600 meant that it required an engine with approximately 100 less horsepower, further increasing fuel economy.

[5][7] Along with its sloped hood, the aerodynamic design of the T600 semitractor utilizes several features that mark a major shift away from the Kenworth W900.

Along with a smaller turning radius (nearly 25% less than a standard conventional[4][7]), the configuration allowed for designers to add longer front springs to the suspension, improving weight distribution and ride.

Another change involved the addition of turn signal repeaters added to rear-facing portion of the front fenders.

Built with a slightly shortened hood (for a 112-inch BBC length), the T400 was designed for regional shipping and local delivery applications.