1996 HMMWV M998 Series Unit Maintenance Manual Volume 2 (TM 9-2320-280-20-2)

Description

1996 HMMWV M998 Series Unit Maintenance Manual Volume 2 (TM 9-2320-280-20-2)

This is Volume 2 of 3 of the Unit Maintenance Manual for the HMMWV (High Mobility Multipurpose Wheeled Vehicle) M998 series of 1-1/4 ton, 4×4 utility trucks. It covers Chapters 3 through 9 in full, taking the unit-level mechanic through engine systems, the complete electrical system, transmission and transfer case, propeller shafts, axles, suspension, service and parking brakes, wheels and steering, and frame repairs. The original January 1996 edition is presented here with the Change 1 and Change 2 updates incorporated, so the procedures, torques and illustrations reflect the later production configurations as well as the original setup.

File Details

• Manual type: Unit Maintenance Manual, Volume 2 of 3
• Document numbers: Army TM 9-2320-280-20-2, Air Force TO 36A12-1A-2092-1-2, Marine Corps TM 2320-20/7B
• Equipment: Truck, Utility, Cargo/Troop Carrier, 1-1/4 Ton, 4×4 – M998 series HMMWV
• Chapters covered: 3 through 9
• Language: English
• Page count: 952 pages
• File format: PDF
• Original publication date: 31 January 1996
• Updates included: Change 1 (14 September 1998) and Change 2 (30 June 1999)

Chapters Covered in This Volume

• Chapter 3 – Engine Systems Maintenance: lubrication system (dipstick tube, filler tube, filter adapter, oil service, oil pan, cooler lines, oil cooler assembly, CDR valve and hoses), fuel system (air cleaner, filter element, air horn, air restriction gauge, fuel pump, fuel tank, supply/return lines, vent line and filter, filler cap and spout, fuel filter, glow plug, injection line brackets), accelerator system (linkage, pedal, idle speed, hand throttle cable), exhaust system (tailpipe, muffler, catalytic converter, crossover pipe, heat shields, exhaust manifolds), cooling system (servicing, radiator and fan shroud, surge tank, hoses, thermostat, water pump and adapter plate, water crossover, fan drive, drivebelts, tensioner)
• Chapter 4 – Electrical System Maintenance: generating and protective control box system (60/100/200 ampere alternators, regulators, cables, pulleys, mounting brackets, protective control box, distribution box, dual voltage alternator and regulator systems), starter and starting control system (rotary switch, starter, circuit breaker), instruments, sending units, switches and horn (instrument cluster and panel, gauges, tachometer, speedometer, warning lamps, switches, horn), transfer case and transmission electrical (indicator switches and lamps, transmission circuit breakers, relays, TCM, E-PROM, kick-down switch, TP sensor, speed sensors), lighting system (service headlight, blackout drive light, composite lights, side marker lights, directional signals, stoplight switches, backup lights), battery system (cables, terminal clamps, power feed through stud, buss bar, starter power cables, holddown, tray, slave receptacle, shunt, hood harness, connector repair), ambulance electrical system (ceiling lights, spotlights, control boxes, NBC control box and harness, interior lighting, antenna and intercom cables, 200 ampere alternator packages, heat/vent control panels)
• Chapter 5 – Transmission and Transfer Case Maintenance: transmission service (draining, filter, fluid), oil cooler lines, by-pass valve, dipstick tube, neutral start switch, shift controls housing assemblies, transmission shift rod, modulator assembly and link, vent line, converter housing covers, transmission mount, road test, transfer case shift rod, speedometer driven gear, vent line, oil seals
• Chapter 6 – Propeller Shafts, Axles, and Suspension Maintenance: front and rear propeller shafts, universal joint repair, halfshafts, geared hub side cover, geared hub replacement, geared hub input and spindle seals, spindle bearing adjustment, wheel studs, differential vent line, geared hub vent lines, steering stop, air lifting bracket, differential cover, stabilizer bar and link, radius rod, upper and lower ball joints, upper and lower control arms, coil springs, shock absorbers
• Chapter 7 – Brake System Maintenance: parking brake system (adjustment, caliper and rotor, lever, cable, rod, heat shields), service brake system (bleeding, pads, calipers, master cylinder, hydro-boost, lines, pedals, proportioning valve, rotor), rear dual service/parking brake system (pads, calipers, cables, rod, adjustment)
• Chapter 8 – Wheels and Steering Maintenance: wheel and runflat system (jacking, wheel replacement, tire/wheel/runflat maintenance for bias and radial tires, runflat compressor belts, inner rim studs, balancing, front toe-in and rear toe-out alignment), steering components (steering wheel, pitman arm, center link, tie rod and tie rod ends, idler arm, steering column, intermediate shaft, steering gear, U-joints, close-off, power steering pump, hydraulic hoses, control valve, cooler hoses, cooler, bleeding, relief valve)
• Chapter 9 – Frame Maintenance: front bumper and towing brackets, frame extension, tiedown ring, radiator front mount bracket, rear bumper brace, rear crossmember brace, rear bumper, inner mounting bracket, towing pintle, lifting shackle, receptacle mounting bracket, transmission mount crossmember, rear crossmember

This HMMWV M998 series unit maintenance manual volume gives the unit-level mechanic the full removal, disassembly, cleaning and inspection, assembly and installation procedures for every major system on the truck. The scope is broad: engine lubrication and fuel systems, the complete 24-volt electrical system including alternator and starting circuits, the transmission and transfer case, driveline and suspension, hydraulic and mechanical brake systems, wheels with runflat assemblies, steering, and the frame. Each task is structured with initial setup, tools and materials, equipment conditions, step-by-step procedures with torque values and clearances, and follow-on task references so the work can be scheduled in sequence without missing a step. Wiring diagrams, exploded views, sealant diagrams, and tightening sequences are placed with their procedures, which is what separates a usable unit maintenance manual from a general repair guide.

What This Volume Covers for the M998, M998A1, M1038, M1038A1, M1097, M1097A1, M1097A2 and M1123

Volume 2 is the middle volume of the three-part unit maintenance set. Volume 1 carries Chapters 1 and 2 (general information and troubleshooting), and Volume 3 carries Chapters 10 through 13 and the appendices. Having this volume means the engine and driveline work, the electrical diagnostics, the transmission and transfer case service, brake overhaul, and steering and frame repair are all covered in one document for the cargo/troop carrier, heavy variant, and up-armored HMMWV configurations. The towing carrier, armament carrier, S250 shelter carrier, and ambulance variants (M966, M996, M997, M1035, M1025, M1026, M1043, M1044, M1037, M1042, and their A1/A2 updates) are also addressed where their systems differ – particularly in the ambulance electrical section and the rear dual service/parking brake section for A2 vehicles.

Why This Manual Matters

Torque values on the HMMWV are not guesswork: the spindle retaining nut, halfshaft capscrews, ball joint locknuts, hub locknuts, brake caliper capscrews, and wheel locknuts all have published specifications that must be followed or the components will fail prematurely. This manual supplies those values, the tightening sequences for the wheel locknuts and the caliper halves, the sealant and adhesive application points, and the adjustment procedures for the parking brake, throttle position sensor, drivebelts, and toe-in and toe-out alignment. It also flags the safety warnings – drycleaning solvent use, compressed air limits, exhaust poisoning, wheel assembly inflation limits, and the danger of mixing radial and bias tires – that a mechanic needs to work on the truck without injury.

Instant PDF Delivery

The complete 1996 HMMWV M998 series unit maintenance manual Volume 2 (TM 9-2320-280-20-2) is delivered as an instant PDF download after checkout. No shipping, no waiting, no paper to lose. Read it on a laptop, tablet or phone in the bay, print only the pages you need for the job, and keep the full set on hand for every M998 series truck you service. Whether you are chasing an electrical fault, replacing a geared hub, adjusting the parking brake, or rebuilding a propeller shaft, this volume carries the procedures and specifications to do it correctly.