1986 GMC Topkick Operator Manual

The 1986 GMC Topkick is a medium-duty truck designed for commercial and industrial applications. This operator manual covers the C5H042 (4x2) and C5H062 (6x2) models with GVWR ratings from 25,500 to 35,000 lbs. Features include diesel and gasoline engine options, manual and automatic transmissions, hydraulic brakes with air assist, power steering, and comprehensive instrumentation. Below are key sections for safety, operation, maintenance, specifications, and troubleshooting.

1. Vehicle Identification 2. Controls and Instruments 3. Starting and Operating 4. Specifications 5. Routine Maintenance 6. Fuel System 7. Electrical System 8. Brake System 9. Tires and Wheels 10. Troubleshooting 11. Warranty Information

Vehicle Identification

Locate your vehicle identification number (VIN) on the driver's side dashboard visible through the windshield and on the certification label on the driver's door edge.

Component	Location
VIN Plate	Driver side dashboard
Certification Label	Driver door edge
Engine Serial Number	Right side of engine block
Transmission ID	Transmission housing
Axle Identification	Axle housing

Controls and Instruments

Familiarize yourself with all controls before operating the vehicle.

Control	Function
Ignition Switch	Starts engine and controls electrical systems
Gear Selector	Manual transmission or automatic shift control
Parking Brake	Spring-applied parking brake lever
Headlight Switch	Controls exterior lighting
Wiper/Washer	Windshield wiper and washer control
Instrument Cluster	Speedometer, tachometer, gauges, warning lights
Air Controls	Heating, ventilation, and air conditioning
Auxiliary Switches	Optional equipment controls

Starting and Operating

Proper starting and operating procedures ensure vehicle longevity and safety.

Pre-start Inspection: Check fluid levels, tires, lights, and brakes.
Starting Procedure: Depress clutch (manual), turn ignition to start position.
Warm-up: Allow engine to reach operating temperature before driving.
Shifting: Use proper gear selection for load and road conditions.
Braking: Apply service brakes gradually; use engine braking when descending grades.

WARNING! Always perform pre-trip inspection. Never operate with warning lights illuminated.

Specifications

GVWR: 25,500 - 35,000 lbs
Engine Options: 6.0L V8 gasoline, 6.2L diesel
Transmission: 5-speed manual, 4-speed automatic
Brakes: Hydraulic with air assist, front disc/rear drum
Steering: Power assisted recirculating ball
Fuel Capacity: 40 gallons standard
Wheelbase: 135 to 235 inches
Cab Configuration: Conventional cab

Routine Maintenance

Follow scheduled maintenance intervals for optimal performance.

Daily: Check engine oil, coolant, tires, lights
Weekly: Inspect brakes, steering components
Monthly: Check battery, belts, hoses
3,000 miles: Change engine oil and filter
6,000 miles: Lubricate chassis components
12,000 miles: Replace fuel filter, inspect brakes

CAUTION! Use only recommended fluids and filters. Record all maintenance.

Fuel System

The fuel system requires regular maintenance for proper operation.

Component	Maintenance Interval
Fuel Filter	Replace every 12,000 miles
Fuel Lines	Inspect for leaks monthly
Fuel Tank	Drain water separator weekly
Injection System	Professional service as needed

Tip: Use clean, dry fuel from reputable sources.

Electrical System

Maintain proper electrical system function with regular checks.

Battery: Check terminals for corrosion, fluid level monthly
Alternator: Ensure proper belt tension and output
Lights: Check all exterior and interior lights weekly
Fuses: Locate and identify all fuse panels
Wiring: Inspect for damage or wear

WARNING! Disconnect battery before performing electrical work.

Brake System

The hydraulic brake system with air assist requires regular inspection.

Check brake fluid level weekly
Inspect brake pads and linings monthly
Test parking brake function daily
Bleed brake system annually or as needed
Inspect air system components

CAUTION! Brake failure can cause serious injury. Maintain system properly.

Tires and Wheels

Proper tire maintenance ensures safety and fuel efficiency.

Tire Size	Inflation Pressure	Rotation Interval
8.25R20	90 PSI front, 80 PSI rear	10,000 miles
9.00R20	95 PSI front, 85 PSI rear	10,000 miles
10.00R20	100 PSI front, 90 PSI rear	10,000 miles

Tip: Check tire pressure when cold for accurate readings.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel, electrical, or battery issue	Check fuel level, battery charge, starter operation
Poor fuel economy	Dirty air filter, misalignment	Replace air filter, check wheel alignment
Brake pull	Uneven brake wear, alignment	Inspect brakes, check alignment
Electrical issues	Battery, alternator, wiring	Test battery and charging system
Transmission problems	Low fluid, linkage adjustment	Check fluid level, adjust linkage

Service: Contact authorized GMC dealer for major repairs.

Warranty Information

1986 GMC Topkick vehicles are covered by a 12-month/unlimited mileage warranty against defects in materials and workmanship. Warranty coverage requires proper maintenance and operation. Keep all service records. For warranty claims, contact your authorized GMC dealer with proof of purchase and maintenance records.

Customer Assistance: 1-800-GMC-8782 • GMC Truck Division, General Motors Corporation