🏷️ Basic Information

Make:

GMC

Model:

C1500

Year:

1991

Product Type:

Service & Repair Manual Software

👋 Introduction

Market Position:

Provides essential technical documentation for owners of 1991 GMC C1500 trucks seeking to perform maintenance and repairs themselves.

Target Audience:

DIY mechanics, home garage enthusiasts, and professional automotive technicians looking for reliable factory-level repair data for their 1991 GMC C1500.

Competitive Analysis:

Offers a more convenient and often more affordable alternative to outdated printed manuals, with instant online access across multiple devices.

Information Source:

Licensed information derived from OE (Original Equipment) materials, ensuring accuracy and authenticity for repair procedures.

Key Features:

Officially licensed, derived from OE materials, year-round access, compatible with PC/laptop/smartphone/tablet, 1-year access included with purchase.

Licensing:

Officially licensed product, ensuring the legality and authenticity of the repair information provided.

📋 Manual Details

Coverage Areas:

Comprehensive repair and service information for the 1991 GMC C1500

Page Count:

Not Specified (Online Access)

Manual Type:

Online Service and Repair Manual

Language:

English

Format:

Web-based Software (accessible via browser)

📖 Manual Coverage

Systems Covered:

Engine, Drivetrain, Brakes, Suspension, Steering, Electrical System, HVAC, Body and Frame, Wiring Diagrams, Diagnostic Procedures

Electrical System:

Complete coverage of the 1991 GMC C1500's electrical system, including battery, charging system, starting system, ignition system, lighting, instrumentation, power accessories, and diagnostic flowcharts.

Suspension Steering:

Front independent suspension (SLA type), rear leaf spring suspension. Covers ball joints, tie rods, steering gearbox/rack, shock absorbers, and alignment specifications.

HVAC System:

Covers air conditioning system operation, refrigerant types (R12 for this era), compressor, evaporator, condenser, heater core, and blower motor service.

Bodywork Frame:

Includes procedures for body panel alignment, door and window regulator repair, bumper service, and basic frame inspection. Also covers corrosion protection details.

Wiring Diagrams:

Complete and detailed wiring diagrams for all vehicle systems, essential for diagnosing electrical faults and performing modifications.

Procedures Included:

Scheduled Maintenance, Routine Inspections, Troubleshooting, Component Repair, System Diagnostics, Overhaul Procedures, Wiring Harness Repair, Component Replacement

Engine Repair Procedures:

Detailed procedures for engine overhaul, including cylinder head removal/installation, piston and connecting rod service, crankshaft and bearing service, camshaft and valve train maintenance, and oil pump replacement.

Brake System Repair:

Front disc brakes, rear drum brakes. Procedures include pad/shoe replacement, caliper/wheel cylinder service, brake fluid flushing, and parking brake adjustment.

Troubleshooting Guides:

Extensive troubleshooting sections with symptom-based diagnostics, fault code interpretation (if applicable to the vehicle's diagnostic capabilities), and step-by-step diagnostic flowcharts.

Diagnostic Tools Usage:

Guidance on using common diagnostic tools and techniques relevant to the 1991 C1500, such as multimeters and specific test equipment.

Technical Depth:

Factory-derived, OE quality information for detailed diagnostics and repair, suitable for DIY enthusiasts and professional technicians

Diagnostic Capabilities:

In-depth diagnostic procedures for identifying and resolving common and uncommon faults across all major vehicle systems, utilizing technical specifications and troubleshooting trees.

Torque Specifications:

Comprehensive torque specifications for all critical fasteners in engine, drivetrain, chassis, and body components, ensuring proper assembly and safety.

Component Diagrams:

Detailed exploded views and diagrams for most components, aiding in identification and reassembly during repairs.

Rebuild Procedures:

Comprehensive instructions for rebuilding major components like the engine, transmission, and differential, including specifications for clearances and tolerances.

📊 Manual Specifications

File Format:

N/A (Web-based)

Accessibility:

Accessible via a web browser on any internet-connected device, providing instant access to information.

Device Compatibility:

Works on any device with a modern web browser and internet connection, including Windows PCs, Macs, Android tablets, iPads, and smartphones.

Search Functionality:

Likely includes a robust search function for quickly finding specific information within the manual's extensive content.

Print Quality:

N/A (Digital Access)

Binding Type:

N/A (Digital Access)

Paper Type:

N/A (Digital Access)

⚙️ Engine Specifications

Engine Options:

4.3L V6 (VIN 'X'), 5.0L V8 (VIN 'H'), 5.7L V8 (VIN 'K'), 7.4L V8 (VIN 'P') - Manual covers all primary engine offerings for the C1500 series.

Engine Codes:

VIN 'X' (4.3L V6), VIN 'H' (5.0L V8), VIN 'K' (5.7L V8), VIN 'P' (7.4L V8). Manual provides specific data for each.

Engine Description:

Features robust V6 and V8 gasoline engines known for their durability and torque, suitable for hauling and towing applications.

Horsepower Torque:

Specific HP and Torque figures vary by engine option. For example, the 5.7L V8 typically produced around 175-195 HP and 300-315 lb-ft of torque. Manual provides detailed specifications for each engine.

Fuel System Type:

Fuel Injection (TBI - Throttle Body Injection for V6/5.0L V8, TPI - Tuned Port Injection or MPFI - Multi-Port Fuel Injection for 5.7L/7.4L V8). Manual details fuel pump pressures, injector specifications, and diagnostic procedures.

Fuel Pump Pressure:

Typically around 10-13 PSI for TBI systems. Manual will specify exact pressures and testing methods.

🔧 Transmission

Standard Transmission:

Manual (e.g., 4-speed Saginaw SM465, 5-speed NV4500 optional on some configurations).

Manual Transmission Types:

SM465 (4-speed, heavy duty), NV4500 (5-speed, optional) and related clutch system information.

Optional Transmission:

Automatic (e.g., 700R4/4L60 4-speed, TH400 3-speed heavy-duty option).

Automatic Transmission Types:

700R4 (later designated 4L60), TH400 (heavy duty option). Covers service, overhaul, and adjustments.

Transmission Features:

Manual covers clutch operation, transmission fluid type and capacity (e.g., Dexron-III for automatics), shift linkage adjustment, internal component repair, and torque converter information.

📐 Dimensions

Wheelbase:

Various wheelbases available, including 117.7 inches (Standard Cab, Fleetside) and 131.5 inches (Long Bed, Extended Cab). Manual provides chassis and body dimension details.

Body Styles:

Fleetside (Styleside) Bed, Stepside Bed, Regular Cab, Extended Cab.

Tire Sizes:

Common sizes include P205/75R15, P235/75R15, and P245/75R16, depending on configuration. Manual provides detailed tire and wheel specifications, including recommended pressures.

Wheel Bolt Pattern:

Typically 6x5.5 inches (6x139.7mm).

Curb Weight:

Varies significantly based on configuration (engine, cab, bed, drivetrain). Typically ranging from 3,800 to 5,000 lbs. Manual provides specific GVWR and payload capacities.

🛡️ Safety Features

Safety Ratings:

NHTSA ratings for 1991 vehicles may be limited. Manual provides information on brake system diagnostics and repair, steering system maintenance, and tire specifications critical for safe operation.

Passive Safety Features:

Seat belts, reinforced cab structure. Manual details seat belt system inspection and repair.

Active Safety Features:

Power assisted brakes, power steering. Optional rear-wheel ABS. Manual details inspection and maintenance for these systems.

💡 Technology Features

Infotainment System:

Basic AM/FM radio, cassette player. Optional premium sound systems. Manual covers basic electrical diagnostics for the audio system.

Driver Assistance Features:

ABS (Anti-lock Braking System) often available on rear wheels, potentially on all four depending on configuration. Manual covers ABS system diagnostics.

Connectivity Features:

N/A (No integrated connectivity features common in modern vehicles).

🔧 Maintenance

Recommended Oil Change:

Typically every 3,000-5,000 miles or 3-6 months, depending on driving conditions. Manual provides detailed service schedules for all major components.

Transmission Fluid Change:

Typically every 30,000-50,000 miles for automatic transmissions, or as per specific driving conditions. Manual provides detailed fluid change intervals and procedures.

Spark Plug Replacement:

Typically recommended between 30,000 and 60,000 miles, depending on spark plug type. Manual provides specific intervals and gap settings.

Engine Oil Type:

API Service SG or SG/CD. Viscosity grades typically 5W-30, 10W-30, or 10W-40 based on ambient temperature. Manual lists specific capacities and types for all fluids (coolant, brake fluid, power steering fluid, transmission fluid, differential fluid).

Coolant Type:

Conventional Green Ethylene Glycol based coolant. Manual specifies capacity and type.

Differential Fluid Type:

API GL-5. Viscosity typically 75W-90 or 80W-90. Manual specifies capacities for rear-wheel drive and four-wheel drive differentials.

Brake Fluid Type:

DOT 3. Manual specifies correct type and bleeding procedures.

Common Wear Items:

Potential issues include distributor cap/rotor wear, fuel pump reliability, intake manifold gasket leaks (on some V8s), and suspension component wear (ball joints, bushings). Manual provides diagnostic steps for these.

Common Electrical Issues:

Corrosion in electrical connectors, fuel gauge sender unit failure, and intermittent operation of power accessories. Manual's wiring diagrams are crucial for diagnosis.

📚 Vehicle History

Brand Heritage:

GMC (General Motors Truck Company) has a long history of producing robust and capable trucks, with the C/K series being a cornerstone of their light-duty pickup truck line.

Model Evolution:

The 1991 C1500 is part of the third generation of GMC's C/K trucks (GMT400 platform), which introduced significant aerodynamic styling updates and improved chassis design over its predecessors.

Platform Changes:

The GMT400 platform represented a significant modernization with independent front suspension, a wider track, and improved aerodynamics compared to the previous C/K generation.

Production Platform:

GMT400 platform, produced from 1988-1998. The 1991 model year represents an evolution within this generation.