TM 9-2320-272-24-4

Introduction

This manual, TM 9-2320-272-24-4, provides comprehensive maintenance information for the 5-ton M939 US Military Trucks. As Volume 4 of 4 in the Direct / General Support Manual Series, it is an essential resource for maintaining these robust vehicles.

The M939 series trucks are heavy-duty 6x6 vehicles, designed to transport up to 10,000 pounds of cargo across all terrains and in all weather conditions. Originally developed in the 1970s to supersede the M39 and M809 series, approximately 44,590 units were produced. This manual is specifically compiled to assist private owners and maintenance personnel in the proper upkeep and repair of their M939 series vehicles.

Figure 1: Front cover of the TM 9-2320-272-24-4 Maintenance Manual, depicting an M939 series truck.

Product Overview: M939 Series Truck

The M939 series represents a family of 5-ton, 6x6 medium tactical trucks. These vehicles are integral to military logistics, designed for high mobility and durability in demanding environments. Key characteristics include:

• Payload Capacity: 10,000 pounds (5 tons) of cargo.
• Drivetrain: 6x6 all-wheel drive for superior off-road capability.
• Purpose: Primarily cargo transport, but also adapted for various specialized roles.
• Historical Context: Successor to the M39 and M809 series, with significant production numbers.

Understanding the fundamental design and operational purpose of the M939 is crucial for effective maintenance, as detailed in this manual.

Using This Manual: Setup and Navigation

This manual is structured to facilitate efficient access to maintenance procedures. Before commencing any work, familiarize yourself with the following:

1. Section Identification: Each major section addresses a specific system or type of maintenance. Refer to the chapter titles for quick navigation.
2. Safety Precautions: Always review the safety warnings and precautions at the beginning of relevant sections. Personal protective equipment (PPE) and safe work practices are paramount.
3. Tool and Equipment Lists: Procedures often list required tools and equipment. Ensure all necessary items are available before starting.
4. Illustrations and Diagrams: Detailed figures and schematics are provided to aid understanding. Cross-reference text with accompanying visuals.
5. Reference to Other Volumes: As Volume 4, this manual may refer to information contained in Volumes 1, 2, or 3. Ensure access to the complete series for comprehensive support.

Proper setup involves having a clean workspace, adequate lighting, and all required materials at hand.

Operating Procedures (Manual Usage)

While this is a maintenance manual, its "operation" pertains to how it should be used to guide vehicle operations and maintenance tasks. Follow these guidelines:

• Pre-Operation Checks: For routine checks, consult the relevant sections on daily or weekly inspections.
• Fluid Levels: Procedures for checking and replenishing engine oil, coolant, transmission fluid, and other vital fluids are detailed.
• Tire Pressure: Refer to the chassis section for correct tire inflation specifications and inspection procedures.
• Lighting and Electrical Systems: Instructions for verifying the functionality of lights, indicators, and other electrical components are included.

Always perform a thorough review of the applicable section before operating the vehicle or performing any operational checks.

Maintenance Procedures

This volume focuses on direct and general support maintenance, covering a wide array of tasks necessary to keep the M939 series truck in operational condition. Maintenance is categorized by system for clarity.

Engine System Maintenance

Detailed procedures for the engine, including:

• Oil and Filter Changes: Step-by-step instructions for draining, refilling, and replacing oil filters.
• Fuel System Servicing: Maintenance of fuel filters, lines, and injection components.
• Cooling System: Checks for coolant levels, radiator condition, hose inspection, and thermostat replacement.
• Air Intake System: Cleaning and replacement of air filters, inspection of intake manifold.

Chassis and Drivetrain Maintenance

This section covers the structural and power transmission components:

• Suspension System: Inspection of springs, shock absorbers, and suspension linkages.
• Brake System: Adjustment, inspection, and replacement of brake pads, drums, lines, and air brake components.
• Steering System: Lubrication, adjustment, and inspection of steering linkages and power steering components.
• Axles and Differentials: Fluid checks, lubrication, and inspection for wear.
• Tires and Wheels: Rotation, balancing, and inspection for damage or wear.

Electrical System Maintenance

Guidance on the vehicle's electrical components:

• Battery Servicing: Inspection, cleaning, and testing of batteries and terminals.
• Alternator and Starter: Testing procedures and replacement instructions.
• Wiring and Connectors: Inspection for damage, corrosion, and proper connection.
• Lighting and Instrumentation: Troubleshooting and replacement of bulbs, fuses, and gauges.

Always disconnect the battery before working on electrical systems to prevent injury or damage.

Troubleshooting Guide

This manual includes detailed troubleshooting charts to assist in diagnosing common issues. When encountering a problem:

1. Identify the Symptom: Clearly define the problem (e.g., "Engine cranks but won't start," "Brakes feel spongy").
2. Locate Relevant Chart: Navigate to the troubleshooting section corresponding to the affected system (e.g., Engine, Brakes, Electrical).
3. Follow Diagnostic Steps: The charts typically list possible causes and corrective actions. Follow these steps systematically.
4. Test and Verify: After performing a corrective action, test the system to ensure the problem is resolved.

For complex issues, it is recommended to consult with experienced personnel or refer to specialized diagnostic equipment if available.

Specifications

Key specifications for the TM 9-2320-272-24-4 manual (Volume 4 of 4):

Figure 2: Back cover of the manual, displaying ISBN and barcode information.

Warranty and Support

This document is a reprint of an official US Army technical manual. As such, it does not come with a traditional manufacturer's warranty for the content or the vehicle it describes. The original content reflects military standards and practices from June 1998.

For inquiries regarding the physical publication (e.g., printing quality, binding), please contact the publisher, Ocotillo Press. For historical or technical questions related to the M939 series truck, it is recommended to consult military vehicle enthusiast communities or specialized historical archives.

The ISBN-13 for this publication is 978-1954285682.