1939–1954 Farmall H, HV, W-4, O-4, OS-4, I-4, U-4 and IU-4 Tractor and Power Unit Service Manual (GSS-5032)

International Harvester publication GSS-5032 covers the 1939–1954 Farmall H, HV, W-4, O-4, OS-4, I-4, U-4, and IU-4 tractors and power units. This factory service manual documents their shared 152-cubic-inch four-cylinder engine and the differences in chassis, controls, and attachments.

Text search and service charts: The PDF is partially searchable through an existing OCR layer. Some pages and drawing labels have no searchable text, and recognition errors affect others. There are no embedded PDF bookmarks; small service-chart annotations require magnification.

• Engine repair: Cylinder-head and valve service, piston and connecting-rod inspection, dry-liner sleeve replacement, crankshaft bearings, and timing-gear alignment.

• Fuel and governor: IHC D-10 carburetor adjustment and troubleshooting, float-level checks, governor linkage settings, and oil-washed air-cleaner service.

• Cooling and lubrication: Water-pump removal, repacking, and reassembly, bypass-thermostat operation, oil-pump inspection, and system schematics.

• Ignition and electrical equipment: IHC H-4 magneto timing, generator regulation, cutout-relay operation, starting-motor specifications, battery data, and lighting-switch resistance values.

• Clutch and transmission: Spring-loaded and overcenter clutch adjustment, removal and assembly, plus transmission dismantling, bearing service, and reassembly.

• Chassis and final drive: Differential assembly, bevel-gear contact and backlash adjustment, brake equalization, steering components, wheel bearings, power take-off, and belt pulley.

Originally prepared for student servicemen and International Harvester's Blue Ribbon Servicemen, this manual supports workshop training and service work involving precision measurements and mechanical adjustments.

Engine Repair and Cooling-System Changes

Cylinder-head and valve assemblies differ between high-compression gasoline, gasoline-distillate, and kerosene engines. Piston, connecting-rod, crankshaft, and camshaft bearing specifications support internal engine repair, with component-specific torque, fit, and clearance data.

The sleeve-replacement section identifies puller SE-1213 and describes dry-liner replacement without subsequent honing or boring. Illustrations include the engine lubrication schematic, cooling-system schematic, and water-pump cross section.

Pressure-radiator production changes are identified at FBH-115030 for H, WBH-4849 for W-4, OBH-4849 for O-4, and IBH-4849 for I-4. These references help distinguish original cooling configurations before selecting radiator and heat-indicator parts.

Carburetor Diagnosis and Electrical Service

The D-10 section distinguishes 50981 DA carburetors for high-compression gasoline engines from 45108 DB units for gasoline-distillate and kerosene engines. A sectional carburetor view identifies the metering and idle circuits.

Troubleshooting covers hard starting, missing under load, excessive fuel consumption, power loss, and poor acceleration. It relates these symptoms to compression, ignition, fuel level, air leaks, and governor operation, helping narrow the cause before carburetor repair.

Electrical coverage includes charging-output data and starter no-load and locked-torque specifications. Flywheel ring-gear fitting includes a warning that uncontrolled heat can destroy the gear's temper. Detailed magneto service is referred to the separate Serviceman's Guide on Magnetos, Manual No. 1; electrical wiring diagrams are not included.

Clutches, Gearbox, and Model-Specific Final Drives

Clutch coverage includes release-lever inspection and settings, with a separate adjustment for the I-4 clutch brake. For complete clutch overhaul, the text refers to CHS-62, Tractor and Power Unit Clutches, which is not included.

The IU-4 description distinguishes the first 100 units with modified Farmall H transmissions from the I-4-based arrangement. Its identification table also provides separate chassis and engine numbers and the IU-4 transmission serial-number series EUBH-501 and up.

Service charts show the standard differential and rear axle separately from the Farmall-HV final drive and rear axle. The differential chart warns that insufficient shimming preloads the bearings and causes rapid wear; the bevel-gear section explains tooth-contact patterns and backlash.

Steering, Brakes, and Attachments

Chassis sections cover steering gears, axle seals, wheel-bearing adjustment, brake testing and equalization, and pneumatic-tire care. PTO coverage identifies early Farmall H countershaft differences and W-4/O-4 serial changes affecting attachment selection.

Attachment tables include belt pulleys and U-4 equipment options. Hydraulic Lift-All is listed as an attachment, but hydraulic-pump overhaul procedures are not included. Reference data also cover model-specific fluid capacities.

Always review standard shop safety protocols and ensure you understand the mechanical load limits before beginning any diagnostic work or teardown.

Printable PDF and Included Pages

One printable English-language PDF contains 67 pages total: 59 numbered pages, including the index and notes page; four unnumbered service-chart pages; a front cover, specifications page, and blank back cover; and one seller-added cover page. All are included in the total.