GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Rear Axle Component Views
Figure 1:

Center and the Right I/P
Object Number: 1430017 Size: LF
(1)Marker Lamp Switch (RQ2 and U86 or RQ2)
(2)High Idle Switch (UF3)
(3)Traction Control Switch (NW9)
(4)Outside Heated Mirror Switch (DB6/DB8)
(5)Exhaust Brake Switch (K40)
(6)Rear Axle Driver Control Switch - Two Speed (HPZ/Automatic Transmission)
(7)Air Suspension Dump Switch (G40/G45/GSJ)
(8)Power Take-Off (PTO) Switch
(9)Driver Information Center (DIC)
Figure 2:

Two Speed Rear Axle Harness, Left Rear View
Object Number: 690061 Size: SF
(1)Rear Axle Shift Relay -- Two Speed
Figure 3:

Rear Differential, Front View
Object Number: 690066 Size: SF
(1)Rear Axle Shift Motor -- Two Speed
Figure 4:

Manual Transmission
Object Number: 953494 Size: LF
(1)Rear Axle Driver Control Switch - Two Speed (HPZ/Manual Transmission) or Two Speed Rear Axle Control Valve (HR2/Manual Transmission)
(2)Backup Lamp Switch
(3)Vehicle Speed Sensor (VSS)