Allis-Chalmers D series  The Allis-Chalmers D series is a line of tractors made by the Allis-Chalmers Manufacturing Company from 1957 to 1969. Most of the D-series tractors, except for the D21, had hand-operated, shift-on-the-go oil clutches, commonly referred to as a hand clutch. Allis-Chalmers marketed this arrangement as the "Power Director". This clutch was in low range when pulled back, neutral in the middle, and high range when pushed forward. It could also be ordered as a forward-reverser, called the "Shuttle Clutch". This hand clutch also "exists" on the D21, but it was not meant for shifting on the go. The D14 was the first D-series model, introduced in 1957 and rated at 34.08 belt and 30.91 drawbar horsepower. The D14 had a gas fuel capacity, and propane fuel capacity. The D14 was made from 1957 to 1960, when it was replaced by the D-15. 17,474 units were made. The D14 weighed about 3,880 pounds. The early D15 was essentially the same as the D14 with the same engine but a higher compression ratio and increased RPMs. The option of power steering was also made available. At serial number 9001 a larger engine was introduced, as well as a few other minor improvements. The D15 had a fuel capacity for gas and diesel, and a capacity for LP gas. 17,434 units were built during their production from 1960 to 1969, with a price of $3,000 in 1967. October 1957, the D-17 was introduced, followed by the D10 and the D12 in 1959, in which year Allis-Chalmers made as many as 50 model configurations of the D10, 12, 14, and 17. The D17 was made in gas, diesel, and LPG versions, its 226-cubic-inch engine turned 1,650 rpm, and was tested at 52.6 belt and 46 drawbar horsepower. 62,540 D-17s were produced during their 10-year run. The diesel D17 had a six-cylinder engine with 262 cubic in. and weighed about 4,660 pounds. The D10 replaced the Model B and were not made with narrow front-ends. Their wide front ends were adjustable. Both models (D10 and D12) were tested at 28.5 belt and 25.8 drawbar horsepower and had 138.7 cubic-inch engines; the only difference between the two was that the D12 had longer front-axle sleeves and a wider front axle adjustment for wider rows. 5,304 D10s were made from 1959 to 1967.