Pressure Switch Manifold
WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
See PRESSURE SWITCH MANIFOLD
under REMOVAL & INSTALLATION in SERVICING - "C" & "K" SERIES (ALLISON) article.