Farmall A/B/AV/BN International A U-2 1939–1952 Service Manual (P/N CHS-27)

This 64-page PDF reproduces an International Harvester dealer service manual for Farmall A, AV, B, and BN tractors, the International A industrial tractor, and the U-2 power unit, with a printed index and 26 navigation bookmarks. Prepared expressly for IH dealers, it is best suited to experienced mechanics working from specification tables, sectional drawings, and concise factory procedures.

• Coverage and identification: Gives serial-number starting points for each tractor and the U-2, separate early BN and U-2 engine ranges, and HA-5/HA-8 altitude-piston suffix identification.
• Engine repair data: Covers cylinder-head and valve service; selectively fitted piston and wet-sleeve work; connecting-rod alignment; crankshaft bearings; camshaft and timing gears; oil-pump inspection; and cooling-system checks.
• Fuel, ignition, and governor work: Details Zenith Model 161 and Marvel Schebler TSX disassembly, inspection, jet identification, float setting, and reassembly, plus IH H-4 breaker service, engine timing, and governor-to-carburetor synchronization.
• Clutch and drivetrain coverage: Explains tractor, U-2, and No. 22 harvester-thresher clutch inspection and adjustment; four-speed transmission and differential disassembly and reassembly; bevel-gear contact setup; brake service; and final-drive and axle-shaft removal.
• Electrical, chassis, and attachments: Provides generator-output and starter fault checks, generator and starter-and-light wiring diagrams, steering and wheel data, attachment tables, and PTO conversion information.
• Illustrated reference: Contains 80 numbered illustrations, including engine sectional views, crankshaft/rod/piston/sleeve and carburetor exploded views, a governor schematic, electrical wiring diagrams, a PTO cross-section, and model-specific dimensional drawings.
• Important scope limits: Full H-4 magneto overhaul and clutch rebuilding are referred to separate Blue Ribbon manuals, and the center-of-book Service Charts listed in the printed index are not present in this PDF.

Model, Engine, and Variant Coverage

The serial table identifies Farmall A from FAA-501, AV from FAAV-48562, B from FAB-3675, International A from IAA-57284, and U-2 chassis from UAA-501. BN coverage is split between FAB-39715-X7 through FAB-48349-X7 and FABN-48459 and up; U-2 engine numbers run from UAA-501 through UAA-7831 and UAAM-7832 and up. The common four-cylinder engine has a 3-inch bore, 4-inch stroke, and 113-cu.-in. displacement. Gasoline, distillate, and kerosene builds are discussed, with natural-gas equipment for the U-2; HA-5 and HA-8 identify 5,000- and 8,000-foot piston configurations. The No. 22 harvester-thresher engine receives its own cooling, governor, carburetor, and clutch notes.

Engine and Fuel-System Repair Depth

The engine chapters cover valve-seat and guide work, piston-ring evaluation, sleeve removal and installation, rod alignment, main-bearing service, crankshaft seals, camshaft removal, timing-mark alignment, pressure-lubrication checks, and oil-pump inspection. Specification blocks supply torque data, fits, wear limits, spring tests, and lubrication information. An oil-filter production change distinguishes engines 501-97937 from 97938 and up, pairing them with improved elements 63858-D and 63855-D.

The sleeve section specifically warns against interchanging pistons among their selectively fitted sleeves or piston pins among pistons; it also calls out the ring-travel ridge because it can damage the piston or a new top ring. The electrical chapter warns that running without a battery while leaving the generator field circuit closed can damage the generator windings.

Separate repair sections for Zenith 161 and Marvel Schebler TSX carburetors cover disassembly, cleaning, calibrated-jet protection, inspection, float-level setting, and reassembly. Jet tables distinguish tractor, U-2, and No. 22 applications for gasoline and kerosene/distillate use. The ignition and governor material adds H-4 breaker-point service, magneto-to-engine timing, firing-order wiring, speed adjustment, surge diagnosis, and governor/carburetor synchronization.

Drivetrain, Electrical, and Chassis Coverage

The drivetrain chapter identifies the selective-sliding spur-gear transmission with four forward speeds and reverse, then covers shaft and gear removal, shift-rail inspection, reassembly, differential service, bevel-pinion position, tooth-contact pattern, and backlash adjustment. Brake adjustment and relining access, axle-shaft removal, final-drive sealing, and the belt-pulley/PTO drive are also addressed. Tables separate early nonstandard 1-1/8-inch PTO equipment from standardized 1-3/8-inch conversion package 66191-D and later attachment combinations.

Electrical diagnosis covers the generator, cutout relay, light switch, wiring, starter, Bendix drive, and battery. Chassis pages cover frame and axle configurations, steering-gear removal and sealing, front and rear wheel arrangements, tire applications, and liquid ballast. The dimensional section supplies model-specific side, front, rear, and drawbar drawings for Farmall A, AV, B, BN, International A, and U-2.

Full H-4 magneto overhaul is referred to Blue Ribbon Service Training Course Manual No. 1 (Form CHS-27), while complete clutch rebuilding is referred to Manual No. 10 (Form CHS-62). The PDF does not contain the unnumbered center-of-book Service Charts referenced by the printed index, and it has no hydraulic-system repair chapter.

Caution: Heavy machinery maintenance carries inherent risks. Always verify procedures and consult a certified heavy equipment mechanic before beginning any teardown or overhaul.