In 1935, John Deere’s management received a wake-up call when its chief competitor, IHC, introduced a diesel tractor, the Model WD-40.

Deere dealers, fearful of losing sales to this more powerful tractor, were clamoring for a response. And Deere characteristically responded by carefully and methodically taking 14 years to design an engine true to its two-cylinder roots.

Who could blame the company? Deere’s large-block two-cylinder gas tractors were powerhouses, turning out very respectable torque in the field. Nonetheless, farmers were quickly warming to the low cost of diesel fuel and envied the high torque of the engines that burned it. So as early as 1936, Deere’s chief engineer, Elmer McCormick, assembled a team to design a two-cylinder diesel.

At first, those engineers worked on a procedure to start the engine on gas. It ran on that fuel until the motor warmed up sufficiently to combust diesel. They dropped that concept, though, exploring instead a 24-volt starter to spin a high-compression engine over fast enough for ignition. In the meantime, they toiled over different combustion chamber designs that would deliver high enough compression to ignite diesel.

By the mid-1940s, the basic engine platform had been set. And Deere engineers had found their answer to the starting issues. Taking a lesson from Caterpillar (which introduced the first successful diesel in 1931), they opted to employ a starter, or pony, gas engine to spin their diesel over.

The result of 14 years’ toil was realized in the Model R. In January 1949, the first R came off the Waterloo assembly line and was immediately shipped to Montana for the wide-open wheat country where beefy diesel tractors were in high demand. 

The diligence Deere engineers put into their diesel paid immediate dividends when the R set fuel economy standards at the Nebraska Tractor Test. And the tractor was a beast at lugging a load. Weighing 7,400 pounds, the R turned out a draft of 6,644 pounds in first gear, developing 45¾ drawbar horsepower.

The R receives much acclaim for being Deere’s first diesel. But the tractor notched up other numbers ones. It was the first Deere tractor equipped with a live independent PTO (which also drove its hydraulic pump) and the first to offer an optional factory cab.

The R certainly was popular with farmers. In production for just five years, the R racked up over 21,000 units sold. True, those numbers pale next to the Model A’s, whose sales topped 320,000. But Deere management realized that the R represented the future of tractor horsepower. So much so that it was replaced by not one, but two models: the 70 and the 80.

The 70 Diesel hit first, in 1953 and before production of the R ceased. The significance of this introduction lies in the fact that the tractor was Deere’s first row-crop diesel.

In the 70’s belly was nestled a 376-cubic-inch two-cylinder diesel even more fuel stingy and powerful than the R’s. When it was tested at Nebraska, the Model 70 established a new fuel-economy record (beating the record set by the R) while recording a 51½ horsepower drawbar pull.

Deere engineers also tweaked the 70’s diesel by adding a new center main bearing for the crankshaft, which kept that shaft in place under load. This addition also provided better engine balance.

The 70’s big brother, the Model 80 Diesel, hit the market in 1955. It incorporated many of the popular features introduced on the 70 such as the Powr-Trol hydraulic system, independent PTO, and power steering.

But the 80 Diesel was in a class by itself. Capable of pulling a 21-foot disk, this green beast delivered a third more power than the Model R, generating 57½ drawbar horsepower. Both the 70 and 80 had updated Pony engines. Gone was the Model R’s two-cylinder unit, replaced with a four-cylinder (V-formation) motor.

True to Deere form, the 80 Diesel established a new fuel economy standard when tested at Nebraska (thus topping its little brother’s record). 

Deere may have taken its time developing a diesel tractor. But by the 1958 introduction of the Models 730 and 830 Diesel, the company’s course was well set as a diesel-engine tractor powerhouse. 

In 1956, the third generation of diesel tractors introduced by John Deere immediately started setting records. The Model 720 Diesel set a new fuel economy record (even beating out crawlers) at the Nebraska Tractor Test while turning out 51 drawbar horsepower. That output placed the 720 Diesel at the top of the market as the most powerful row-crop tractor available.

The 720 was only built for three years. But during that time, 30,675 (in diesel, gas, and LP gas versions) were sold, testifying to its huge popularity with farmers. Its successor, the Model 730, quickly established itself as the most popular of Deere’s 30 Series tractors.

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