This is the original wiring diagram printed by GM for dealer mechanics. You can follow the wiring in your truck from bumper-to-bumper. It will help you to understand connector configurations, and locate & identify circuits, relays, and grounds. Although the schematic is in black and white, the color of each wire is noted. You will not find this diagram in your shop manual. The schematic measures 8.5" x 11" when folded up, and opens up to 11" by 38". The diagram pictured is an example of this type when folded, but is not the actual diagram for your vehicle. Buy now for the best electrical repair info - the factory wiring diagram.
1977 Truck Wiring Diagrams MD14875
This item is original.
11.00 x 8.50 x 0.10 inches
Covers medium duty Chevrolet and GMC conventional truck models C5, C50, C5000, C6, C60, & C6000, with the in-line 6 cylinder engine. This is for right hand drive vehicles only. See my other items for the left hand drive diagram. To verify that this is the correct diagram for your truck, you can check your VIN code. The 2nd digit should be a C for the medium duty conventional cab, the 3rd digit should be an S to indicate the in line 6 gas engine and the 6th digit should be an 7 for the 1977 model year.
1977 Chevrolet 40-60 Medium Duty
1977 GMC Series 4500-6500
1977 Chevrolet 40-60 Medium Duty 1977 GMC Series 4500-6500