1972–1985 Allis Chalmers 616 620 720 & Pow'r Max Tractor Manual & Parts Catalog (P/N TP 500-0504-01-PM-SA)

These two PDFs contain factory repair and parts information for the Allis-Chalmers large-frame garden tractor family. The 129-page repair manual is a reprint combining the previous Volume 1 and Volume 2 material and carries document identifier TP 500-0504-01-PM-SA. The separate 125-page Model 720 Parts Catalog carries Form 9003847 (Aug. 1974). Together, the set totals 254 PDF pages. Written for repair personnel, the material assumes familiarity with tractor controls and shop safety, along with access to suitable lifting, electrical-test, and hydraulic pressure-test equipment.

• Exact cover identification: Model 616, Mfg. No. 2020185; Model 620, Mfg. Nos. 2020303 and 2020304; and Model 720, Mfg. Nos. 1690073, 1690231, and 1690288. The repair text also uses the 4040, 4041, Pow'r Max, and 9020 designations.
• Powertrain procedures cover clutch and drive-shaft service, bevel-gear transmission removal and setup, differential repair, rear PTO drive-unit overhaul, final-drive work, drop housings, and transmission priming.
• The 15 Series in-line hydrostatic unit chapter includes pressure testing, symptom-based troubleshooting, unit removal, three-section disassembly, pump and motor inspection, valve and seal repair, reassembly, priming, and post-repair testing.
• Brake, steering, front-axle, and power-lift sections document linkage adjustment, component removal and inspection, steering-gear bench adjustment, hydraulic control-valve and cylinder service, and oil-cooler inspection.
• Electrical coverage is organized around battery, charging and ignition, starting, lighting and hourmeter, pressure/temperature sender, and electric PTO circuits, with wiring-harness views, circuit checks, and component removal procedures.
• The Model 720 catalog supplies illustrated parts identification for the tractor plus factory-listed mowers, sickle bar, grader, plow, snow equipment, tiller, cultivator, loader, hitches, hydraulic attachments, and hard-top cab.

Model-Specific Repair Detail

The engine section separates the 4040's Onan CCKA 16-1/2 hp unit from the CCKB 19-1/2 hp engine used in the 4041, Pow'r Max, and 9020. Tractor-side engine removal and installation, shrouds, electrical connections, oil-cooler handling, and PTO alignment are covered. Full internal engine disassembly and fuel-pump, carburetor, governor, and muffler repair are referred to the appropriate Onan repair manual—an important scope limit when planning engine work. Flywheel service identifies Onan puller bar Part No. 420A100.

The 9020 procedures further separate Mfg. No. 1690072 from 1690230 and 1690283 for transmission removal, seat and panel arrangements, neutral-start switch work, and front PTO clutch service. These production differences matter before the tractor is opened or parts are selected.

Drivetrain, Hydraulic, and Electrical Reference

Transmission setup is treated as bench work rather than a simple remove-and-replace job. The manual includes a shim color-identification chart, calculated shim selection, bearing and shaft end-play checks, PTO shaft runout checks, and component-specific torque data. The hydrostatic chapter breaks the assembly into charge-pump, pump, motor, and center sections, identifies non-interchangeable valve and valve-plate parts, and pairs the repair procedures with relief-pressure testing and a troubleshooting chart.

Two full electrical wiring diagrams are provided: Figure 69, Electrical Wiring Diagram (4040) and Figure 70, Electrical Wiring Diagram (4041, Pow'r Max, 9020). Supporting material includes model-specific harness views, charging and ignition circuit diagrams, neutral-start switch views, and electrical test specifications.

Illustrated Parts and Diagram Coverage

Representative service illustrations include Figure 31, Transmission; Figure 65, Power Lift Hydraulic Flow Diagram; Figure 106, Circuit Flow Diagram for the hydrostatic system; Figure 114, Selecting Proper Amount of Shim; and Figure 128, Connecting Motor Housing. The repair manual contains more than 120 numbered figures overall.

The parts catalog follows an illustration-left/text-right format through 56 illustrated plates, with item callouts matched to part numbers, quantities, and descriptions. Alphabetical and numerical indexes support part lookup, while the serial-number-location and drive-belt/chain reference close the catalog. Its exploded parts coverage applies to the Model 720 and listed implements; it does not add implement repair procedures for Models 616 or 620.

The hydrostatic section warns that striking the input, output, or control shafts can damage the unit, while paint thinner or acetone-based cleaners can attack O-rings, gaskets, and seals. The manual’s safety rules also call for proper support of lifted tractor assemblies, electrical isolation, and care around fuel, hot components, rotating PTO parts, and hydraulic pressure.