1988 GMC Sierra C K 2500 Manual

The 1988 GMC Sierra C K 2500 is a heavy-duty pickup truck featuring robust V6 and V8 engine options, 4-wheel drive capability, manual and automatic transmission choices, durable chassis construction, and versatile towing capacity. This manual covers operation, maintenance, specifications, and troubleshooting for this classic workhorse vehicle.

1. Vehicle Overview 2. Controls and Instruments 3. Operating Instructions 4. Technical Specifications 5. Maintenance Schedule 6. Fluid Capacities 7. Towing and Payload 8. Troubleshooting 9. Safety Information 10. Warranty Information

Vehicle Overview

The 1988 GMC Sierra C K 2500 combines rugged capability with classic styling, featuring a sturdy frame, powerful engine options, and versatile cargo capacity.

Feature	Description
Engine Options	4.3L V6, 5.0L V8, 5.7L V8, 7.4L V8
Transmission	4-speed manual, 3-speed automatic, 4-speed automatic
Drive Configuration	2WD or 4WD
Bed Length	6.5 ft or 8 ft
Cab Configuration	Regular cab or extended cab
GVWR	8,600 lbs
Braking System	Front disc, rear drum with power assist
Suspension	Independent front, leaf spring rear
Fuel Capacity	25 gallons (standard), 34 gallons (optional)
Towing Capacity	Up to 10,000 lbs with proper equipment

Controls and Instruments

Familiarize yourself with the dashboard controls and instrumentation for safe operation.

Ignition switch: Located on steering column, positions include LOCK, OFF, RUN, START
Headlight switch: Pull-out type with rotary control for parking and headlights
Climate controls: Manual temperature and fan speed controls
Wiper/washer: Multi-speed wipers with intermittent function
Instrument cluster: Speedometer, fuel gauge, temperature, oil pressure, voltmeter
4WD selector: Floor-mounted or electronic shift for 4WD models

WARNING! Always ensure parking brake is engaged when parked on inclines.

Operating Instructions

Proper operation ensures longevity and reliability of your Sierra 2500.

Starting procedure: Ensure parking brake engaged, transmission in Park/Neutral, turn key to START
4WD operation: Stop completely before engaging 4WD modes; avoid dry pavement use
Towing: Use proper hitch equipment; distribute weight evenly; check trailer brakes
Off-road: Engage 4WD Low for steep grades and difficult terrain
Cruise control: Set speed above 25 mph using controls on turn signal stalk

CAUTION! Never shift to Park while vehicle is moving; serious transmission damage may occur.

Technical Specifications

Wheelbase: 131.5 inches (regular cab), 155.5 inches (extended cab)
Overall Length: 194.5 inches (6.5 ft bed), 218.5 inches (8 ft bed)
Width: 76.8 inches
Height: 71.5 inches (2WD), 73.5 inches (4WD)
Curb Weight: 4,200-4,800 lbs depending on configuration
Payload Capacity: 2,500-3,200 lbs
Turning Circle: 43.5 feet
Ground Clearance: 7.5 inches (2WD), 8.5 inches (4WD)
Fuel Economy: 12-15 mpg city, 15-18 mpg highway

Maintenance Schedule

Regular maintenance is essential for optimal performance and longevity.

Service Interval	Required Maintenance
Every 3,000 miles	Oil and filter change, tire rotation
Every 6,000 miles	Lube chassis, check brakes, inspect suspension
Every 15,000 miles	Replace air filter, check PCV valve
Every 30,000 miles	Replace fuel filter, inspect cooling system
Every 50,000 miles	Replace spark plugs, wires, check timing
Every 100,000 miles	Replace timing chain, inspect transmission

Fluid Capacities

Use only recommended fluids and maintain proper levels.

Engine Oil: 5 quarts (with filter)
Cooling System: 16 quarts (with heater)
Automatic Transmission: 12 quarts (total capacity)
Manual Transmission: 3.5 pints
Transfer Case: 2.5 pints (4WD models)
Front Differential: 3.5 pints (4WD models)
Rear Differential: 4.5 pints
Fuel Tank: 25 gallons (standard), 34 gallons (optional)
Brake Fluid: 1 pint

Towing and Payload

Proper loading and towing procedures ensure safety and vehicle integrity.

Maximum payload: 3,200 lbs (check door sticker for specific vehicle)
Maximum towing: 10,000 lbs with weight-distributing hitch
Tongue weight: 10-15% of trailer weight
Trailer brakes: Required for trailers over 1,500 lbs
Weight distribution: Load cargo evenly in bed, secure properly

WARNING! Exceeding rated capacities can cause component failure and loss of control.

Troubleshooting

Common issues and solutions for the 1988 Sierra 2500.

Symptom	Possible Cause	Corrective Action
Hard starting	Weak battery, fuel pump, ignition	Check battery voltage, fuel pressure, spark plugs
Rough idle	Vacuum leak, dirty injectors	Inspect vacuum hoses, clean fuel system
Transmission slipping	Low fluid, worn clutch/bands	Check fluid level and condition, adjust bands
Brake pulling	Stuck caliper, worn pads	Inspect calipers, replace brake components
4WD not engaging	Vacuum actuator, shift motor	Check vacuum lines, test shift motor operation

Safety Information

Important safety considerations for vehicle operation and maintenance.

Always wear seat belts - lap and shoulder belts provided
Children should be properly restrained in rear seating positions
Never exceed GVWR or GAWR ratings shown on door sticker
Maintain proper tire pressure (check door jamb for specifications)
Use jack stands when working under vehicle - never rely on jack alone
Disconnect battery when performing electrical work

CAUTION! Engine components become extremely hot during operation - allow cooling before servicing.

Warranty Information

The 1988 GMC Sierra C K 2500 was originally covered by GM's New Vehicle Limited Warranty. Current warranty status should be verified with GM or current owner. For technical support contact GM Customer Service or authorized dealerships.

Support: Contact local GMC dealership or GM Customer Assistance Center for historical vehicle information and replacement parts availability.