International Harvester 1566 Tractor

The International Harvester 1566 is a large 66 Series row-crop tractor built for heavy 1970s field work. Its turbocharged six-cylinder diesel delivered about 161 tested PTO hp, and it is remembered as a strong, straightforward high-horsepower IH with distinctive 66 Series styling.

International Harvester 1566 specifications

What the 1566 is used for

The 1566 was designed for demanding row-crop work, including primary tillage, large planters, forage equipment, and heavy PTO implements. Its weight, power, and Category II/III hitch suited it to large-acreage farms of its era.

Today, owners commonly use sound examples for tillage, hay and forage work, tractor pulls, and collector events. It remains practical where a two-wheel-drive, 160-hp-class tractor fits the operation.

Why the International Harvester 1566 stands out

The 1566 is notable for combining IH's familiar 66 Series layout with the powerful DT-436 turbo diesel. It has a strong enthusiast following, broad service knowledge, and generally good parts support through aftermarket, salvage, and specialist channels.

Buying a used International Harvester 1566

Check the torque-amplifier shift under load, clutch and PTO operation, hydraulic pressure and remote-valve function, brakes, steering, and rear axle/final-drive condition. Inspect for engine coolant contamination, turbocharger wear, blow-by, and evidence of overheating; verify the serial number and options, since weight and equipment vary. Confirm exact specifications with TractorData.com and serial-number records.

International Harvester 1566 frequently asked questions

How much PTO horsepower does an IH 1566 have?

The commonly cited tested PTO output is about 161 hp, with about 137 tested drawbar hp.

What years was the International Harvester 1566 built?

It was built from 1974 through 1976.

Is an IH 1566 a good used tractor?

It can be a capable, serviceable heavy-work tractor if the engine, torque amplifier, hydraulics, and driveline have been maintained; inspect those systems carefully before purchase.

Specifications are commonly cited figures for general reference; exact figures vary by year and serial number, so confirm against TractorData.com and the machine's records. Values and prices of used tractors vary by condition and region. Page updated Aug 4, 2026.

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