Pennsylvania Route 641 Truck (PA 641 Truck) is an truck route of PA 641 in Fannett Township in Franklin County that bypasses a winding section of PA 641 that crosses Kittatinny Mountain. PA 641 Truck begins at PA 641 by heading east-southeast on two-lane undivided Amberson Road, which is designated as State Route 4006 (SR 4006). The road soon turns to the northeast and runs through a mix of farmland and woodland, with the Pennsylvania Turnpike (I-76) parallel to the northwest. The truck route heads through the community of Laurel Grove before it passes under the Pennsylvania Turnpike. PA 641 Truck curves to the east and runs through farmland before it turns southeast onto Cold Spring Road, still following SR 4006. The road curves to the south as it comes to a bridge over the Pennsylvania Turnpike just west of the Kittatinny Mountain Tunnel. The truck route heads southwest through forested areas as it traverses Kittatinny Mountain. PA 641 Truck reaches its eastern terminus at another intersection with PA 641 between Kittatinny and Blue mountains.