Lesson #14



Differences. The only difference between the M998 and M998A1 cargo/troop carriers and the M1038 and M1038A1 cargo/troop carriers is that the M998 and M998A1 do not have winches and the M1038 and M1038A1 do.

Purpose of the Vehicle. M998, M998A1, M1038, and M1038A1 cargo/troop carriers are used to transport equipment, materials, and/or personnel. The cargo carrier is capable of transporting a payload (including crew) of 2,500 pounds (1,134 kilograms). The troop carrier is capable of transporting a two-man crew and eight passengers. Both use a troop seat kit for troop transport operations. The cargo/troop carrier also has a four-man crew configuration. The M1038 and M1038A1 are equipped with winches. This feature permits recovery operations of similar vehicles.

Performance. Fully-loaded M998, M998A1, M1038, and M1038A1 cargo/troop carriers will climb road grades as steep as 60% (31) and traverse a side slope of up to 40% (22). The vehicle fords hard bottom water crossing up to 30 inches (76 centimeters) without a deepwater fording kit and 60 inches (152 centimeters) with the kit.

Each driver must be thoroughly familiar with the controls, instruments, indicators, and equipment of  the vehicle to which he is assigned. It is best to actually locate all of these items on the vehicle itself.  If possible, print out this lesson and use it as a guide to physically go through the MMMWV.

The Driver's Compartment

1. Rotary Switch:

2. Wait-To-Start Lamp: The lamp illuminates when the glow plugs are activated and goes out when the engine is ready to start.

3. Brake Warning Lamp: The vehicle has a brake warning lamp that illuminates when the parking brake is applied or if a hydraulic imbalance (leak, etc.) exists between the front and rear brake systems.

4. Air Restriction Gauge: This gauge is located on the instrument panel to the right of the rotary switch and directly below the brake warning lamp.

5. Engine Oil Pressure Gauge: This gauge is the upper left gauge of the instrument cluster.

6. High Beam Indicator: This indicator is in the upper center of the instrument cluster and lights up when the headlights are switched to high beam.

7. Coolant Temperature Gauge: The coolant temperature gauge indicates the temperature of the engine coolant. The gauge should read between 190 to 230F for normal operating temperature.

8. Defroster Control Knob: The defroster control knob is the upper control knob to the right of the instrument cluster. It controls the operation of the defroster.

9. Instrument Panel Lights: The instrument panel is illuminated by two lights in the instrument panel, one on each side of the speedometer. These lights have a dim and bright setting that is controlled by the master light switch.

10. Heater Control Knob: The heater control knob is located to the right of the instrument cluster, directly below the defroster control knob. It varies the temperature of the heated air into the vehicle.

11. Heater Fan Switch: The blower motor is controlled by the heater fan switch. The switch has three settings, "HI", "OFF", and "LO", to regulate the heater and defroster air flow.

12. Voltmeter: The voltmeter is the lower, right gauge in the instrument cluster. It indicates the charging level and activity of the battery charging system. It should register in the green area.

13. Speedometer/Odometer: Like most vehicles, the vehicle has a speedometer/odometer to register speed in miles per hour and accumulated mileage.

14. Fuel Gauge: The fuel gauge indicates the amount of fuel in the tank.

15. Hand Throttle: The hand throttle is provided to increase engine speed for use during cold weather starting, winch operation, and deep water fording, and to obtain maximum alternator output for communications/electrical requirements. The hand throttle is not to be used as an automatic speed or cruise control. It does not automatically disengage when the brake is applied. Increased stopping distances and unsafe operation result if the hand throttle is improperly used.

16. Accelerator Pedal: The accelerator pedal, commonly called the "gas" pedal, allows us to control the engine speed with our foot.

17. Service Brake Pedal: The service brake pedal is used to slow or stop the vehicle by depressing the pedal.

18. Dimmer Switch: The dimmer switch is located in the upper left corner of the driver side floor board and is depressed with the foot to select high or low headlight beam.

19. Light Switch: One control that is entirely different from those in civilian cars is the light switch. This switch controls the service lights, parking lights, turn signals, blackout lights, and the horn.

The switch has three control levers:

For normal daylight driving--

For night driving--

For blackout operations--

To illuminate the instrument panel--

To activate parking lights--

20. Directional Signal Lever / Emergency Flasher: For operation of the directional signal indicator or the emergency flasher, the light switch must be turned to either "STOPLIGHT" or "SERVICE DRIVE".

The Driver's Compartment, Secondary View.

21. Directional Signal Lever (Another View): Directional signal lever activates turn signal lights.

22. Warning Hazard Control (Another View): Warning hazard control activates the warning flashers.

23. Horn Button: The horn button is located in the center of the steering wheel and is depressed to activate the horn. Remember, before the horn will operate, the light switch must be on "STOPLIGHT" or "SERVICE DRIVE".

24. Baffle Operating Rods: On the top right side of the dash are two baffle operating rods. The rods open and close baffles to allow or restrict heated air into the crew compartment.

25. Fresh Air Intake Lever: Fresh air intake lever is pulled back to allow fresh air into crew compartment, or pushed forward to close.

26. (STE/ICE-R) Diagnostic Connector: Simplified Test Equipment/Internal Combustion Engine-Reprogrammable (STE/ICE-R) diagnostic connector is attaching point for the vehicle test meter (VTM) to facilitate vehicle electrical and engine systems diagnoses.

27. Transmission Shift Lever: Transmission shift lever is used to select vehicle driving range, "R" (reverse), "N" (neutral), "D" (drive), "2" (second), and "1" (first). The transmission shift lever is located on the driver’s right in the center console and is similar to those found in civilian cars.

The transmission shift lever can be shifted to five positions:

The proper transmission range selection is made in conjunction with transfer case range selection as discussed below.

28. Transfer Case Shift Lever: Transfer case shift lever is used to select vehicle driving range, "L" (low range), "N" (neutral), "H" (high range), and "H/L" (high lock range). The transfer case shift lever, located to the left of the transmission shift lever, is used to select the transfer case driving range. The ranges and their purposes are--

29. Transmission Indicator Lamp: Transmission indicator lamp comes on when ignition switch is turned on,

and goes off when ignition switch is turned off. It is used to flash the diagnostic trouble codes when the transmission control module (TCM) is placed in the diagnostic mode.

30. Transfer case indicator lamp illuminates when transfer case has completed the low-range shift and high lock range shift.

31. Parking Brake Lever: Parking brake lever is used to apply parking brake.   The vehicle is equipped with a mechanical parking brake that works independent of the service brakes (the brake pedal). The parking brake lever is located immediately to the right of the operator’s seat. The brake lever is pulled up to apply the brake and pushed down to release it. The safety release button must be depressed to release the parking brake in the new configuration.

32. Fording control switch (deep water fording kit only) allows operator to select "VENT" during normal operating conditions or "DEEP FORD" for deep water fording.

33. Steering Wheel Lock Cable: Steering wheel lock cable permits the steering wheel to be locked to prevent unauthorized use of vehicle. The lock cable is located to the immediate left of the hand throttle. Because this vehicle does not have an ignition key, this cable permits the steering wheel to be locked to prevent unauthorized use of the vehicle.

34. Windshield Washer/Wiper Control Knob: The windshield washer/wiper control knob is located on the wiper motor at the center top of the windshield. Windshield washer/wiper control knob operates a two-speed electric wiper motor and when depressed operates the windshield washer.

35. Companion Seat: The companion seat is the front passenger seat. It is removed to provide access to the vehicle  batteries.

36. Battery Box Latches: The battery box latches release to permit removal of the companion seat for access to the batteries.

37. Vehicle Batteries: The vehicle batteries are located in the battery box under the passenger seat. The two batteries provide 24 volts of power to the vehicle electrical system.

38. Slave Receptacle: The slave receptacle is located at the outside front of the battery box and is the connecting point for a NATO slave adapter used to slave start the vehicle.

39. Engine Access Cover: Engine access cover is removed to provide access to rear of engine.

40. Radio Rack: Radio rack serves as mounting point for AN/GRC-160 or AN/VRC-12 radios.

41. Microphone Bracket: Microphone bracket serves as mounting point for microphone.

42. Fire Extinguisher Bracket: Fire extinguisher bracket is located under front of driver’s seat and is the stowage location for fire extinguisher. For new configuration vehicles, the bracket is located on the side of the driver’s seat.

43. Wing Head Screws: Wing head screws (two each) secure front access plate for stowage area under driver’s seat.

44. Driver’s Seat Adjusting Slots: Driver’s seat adjusting slots permit driver’s seat to be locked in a forward or rearward position. For the new configuration vehicles, the adjusters are located on front of driver’s seat.

45. Catch Assembly: Catch assembly holds M16A1 rifle safely in place for travel. Adjustable catch assembly configuration holds M16A1 rifle when positioned all the way in or M203 grenade launcher when extended out.

46. Stock Brace: Stock brace holds stock end of M16A1 rifle or M203 grenade launcher in position for travel.

47. First Aid Kit: First aid kit is located underneath the driver’s seat and is used for crew emergency first aid treatment.

48. Jack Retaining Strap: Jack retaining strap (M1097 only) is located behind the driver’s seat and is used to secure the jack firmly to the vehicle floor.

Engine Compartment

49. Power Steering Fluid Reservoir Cap/Dipstick: Power steering fluid reservoir cap/dipstick (located left front of engine) is removed to fill and/or check power steering fluid level.

50. Transmission Oil Dipstick: Transmission oil dipstick (on vehicles without deep water fording kit) is located right rear of engine and removed to check transmission fluid level.

51. Transmission Oil Dipstick: Transmission oil dipstick (on vehicles with deep water fording kit) is located right rear of engine and removed to check transmission fluid level.

52. Transmission Oil Dipstick Tube: Transmission oil dipstick tube (located right rear of engine) is fill point for transmission fluid.

53. Engine Oil Dipstick: Engine oil dipstick (on vehicles without deep water fording kit) is located behind alternator on left side of engine and removed to check engine oil level.

54. Engine Oil Dipstick: Engine oil dipstick (on vehicles with deep water fording kit) is located behind alternator on left side of engine and is removed to check engine oil level.

55. Engine Oil Filler Cap: Engine oil filler cap (located front center of engine) is removed from oil filler neck to add oil to engine.

56. Radiator Drainvalve: Radiator drainvalve (located beneath right front of engine on lower radiator crossover pipe) is turned counterclockwise to drain coolant from the radiator.

57. Coolant Surge Tank Cap: Coolant surge tank cap (located right rear of engine) is removed from surge tank to add coolant to cooling system.

58. Fuel Filter: Fuel filter (located left rear of engine on firewall) filters water from fuel system.

59. Windshield Washer Reservoir Cap: Windshield washer reservoir cap (located left rear of engine) unsnaps to add windshield washer fluid to reservoir.

60. Fuel Filter Drainvalve: Fuel filter drainvalve (located left rear of engine compartment on cowl, beneath and in front of windshield washer reservoir) is draining point for water collected in fuel filter.

61. Master Cylinder Cover: Master cylinder cover (located left of engine) is removed to fill and/or check brake fluid level.

62. Air Cleaner Assembly: Air cleaner assembly (located right rear of engine) houses air cleaner element which filters dirt and dust from air before it enters combustion chamber.

63. Air Cleaner Dump Valve: Air cleaner dump valve when squeezed, releases dirt, mud, or water from air cleaner body assembly.

64. Cargo Tiedowns: Cargo tiedowns (eight each) provide tiedown points for use in cargo operations (M998, M998A1, M1038, and M1038A1 only).

65. Tailgate Chains and Hooks: Tailgate chains and hooks secure tailgate to rear of vehicle body (all except M996, M996A1, M997, M997A1, and M997A2).

66. Tailgate: Tailgate opens and closes to allow access to vehicle cargo area (all except M996, M996A1, M997, M997A1, and M997A2).

67. Lifting Shackles: Lifting shackles (located at front and rear of vehicle) are used to lift or tie down vehicle.

68. Trailer Receptacle: Trailer receptacle provides electrical power for towed equipment.

69. Towing Pintle: Towing pintle (rear bumper) provides connection point for towing.

70. Pintle Pin: Pintle pin locks pintle latch to towing pintle.

71. Pintle Latch: Pintle latch pulls up to open towing pintle and pushes down to lock towing pintle.

72. Windshield Folddown Hinges: Windshield folddown hinges (soft top models only) are used as a hinge point when lowering windshield. Hinge pins are removed when detaching windshield assembly.

73. Hitch Pin and Hinge Pin: Hitch pin and hinge pin are removed to allow windshield to be lowered or detached.

74. Windshield Hinges: Windshield hinges (soft top models only) secure windshield in the raised (up) position with hinge pins installed. Hinge pins are removed when lowering or detaching windshield.

75. Fuel Tank Filler Cap: Fuel tank filler cap (located at right rear side of vehicle) is removed to permit fuel servicing.

76. Hood Latches: Hood latches (one on each side of hood) unlatch to release hood. The hood on this vehicle is heavy and requires some caution when raising and lowering it. Unlike the hood on civilian cars, the hood must be raised and lowered twice every time the vehicle is operated; once for the before-operation checks and once for the after-operation checks.

Apply these steps to raise the hood:


Personal injury or damage to the equipment may occur if the hood is not properly secured in the raised position.

Use the following steps to lower the hood:


Do not pull the rod at the hook. Otherwise, fingers may be injured.

77. Hood Support Rod: Hood support rod supports hood in the raised position.