1939-1952 Farmall A/B/AV/BN International A U-2 Service Manual (64 P.)

Factory-Level Diagnostic Manual: Tractor Official Farmall A, B, AV, BN Tractors & U-2 Power Unit - 1939-1952 Coverage & Repair Procedures Service-Catalog

Specification-Class: Farmall-A, Farmall-AV, Farmall-B, Farmall-BN, International A industrial tractor, Model U-2 Power Unit, No. 22 Harvester-Thresher Engine // Design-Core: 4-cylinder engine systems, transmission and differential architecture, cooling and fuel system logic // Unit-Designations: 64-page technical reference documenting mechanical assemblies and operational specifications from 1939-1952 manufacturing period.

Engineering chapters address the cylinder head design methodology, exploring valve timing specifications and corrosion-resistant materials through documented casting procedures. The manual continues by examining crankshaft bearing arrangements, then progresses to connecting rod assemblies with their tolerance data and lubrication pathways. Fuel carburetor systems receive corresponding attention, with detailed breakdowns of float mechanisms, idle jets, and load compensation methods across both gasoline and distillate-burning variants. The transmission section references gear reduction ratios and bevel gear alignment principles for field adjustments.

Fluid capacities are listed for the transmission case (1-1/2 gallons), engine crankcase (2.5 quarts), and rear axle housings (3 pints per side), establishing proper fill specifications before operation. Installation guidelines are provided for removable cylinder sleeves, precision-type connecting rod bearings, and magnetic ignition components to ensure correct assembly sequences. Maintenance guidelines are included for carburetor service on both Zenith Model 161 and Marvel Schebler TSX units, with systematic disassembly charts identifying main jet sizes, venturi dimensions, and idle passage configurations. OEM guidelines are included for electrical equipment servicing, including generator cutout relay operation, starting motor brush inspection, and battery electrolyte level maintenance protocols.

The document references torque specifications for cylinder head studs, main bearing cap bolts, and flywheel attachment fasteners to ensure proper assembly tension. Comprehensive wiring diagrams illustrate the correct pathway for magneto spark timing, generator field circuit management, and starter motor control circuits. Dimensional drawings for each model variant capture wheel base measurements, drawbar configuration options, and tire rolling radius data across multiple rim and tire size combinations. The manual provides specifications data for the standardized power take-off shaft system (1-3/8" spline diameter), belt pulley rotation speed (1956 r.p.m. at governed load), and optional pulley diameter options ranging from 6-3/4 inches to 10-3/4 inches.

Traveling speed charts document first through fourth gear ratios under rated load conditions, accounting for tire size variations (8-24, 9-24, 8-36, and 9-36 inches) and their corresponding rolling radius measurements. The manual includes specifications for two front axle designs: the lighter tubular construction on Farmall-A models and the heavy-duty adjustable type on Industrial A, along with rear axle housing configurations unique to B and BN variants. Brake system data encompasses band width dimensions (1-3/4 inches by 18 inches), drum braking area (31-1/2 square inches per drum), and clevis adjustment methodology for achieving correct pedal free movement. Detailed assembly diagrams show the interconnection of differential shaft housing configurations, with separate castings on Farmall-B and BN models versus the integrated design of Farmall-A. Cooling system specifications include thermosiphon circulation principles, fan diameter and blade configuration, and radiator shutter operation on kerosene-burning engine variants.

The manual documents torque specifications for multiple fastener categories to ensure proper assembly and cyclic stress resistance. Charts reference governfour governor weight types, spring identification numbers, and spring tension test values under load. Tables list jet identification data for both Zenith and Marvel Schebler carburetors, cross-referencing part numbers with engine variants and fuel types. Serial number identification sections correlate machine chassis numbers with engine serial assignments for accurate parts lookup and service record tracking across all model variants from 1939-1947 production years.