Allis Chalmers D21 Price, Reviews, Specs, Engine Oil Capacity, Weight, Serial Numbers, Attachments, History, Features & Pictures The Allis Chalmers D21 was the first Allis Chalmers tractor to have over 100 horsepower. The upgraded Allis Chalmers D21 II began at serial number 2201 in 1965. Allis Chalmers D21 Row-Crop Tractor was equipped with an Allis Chalmers 3400 diesel … [Read more...] about Allis Chalmers D21 Price, Specs, Review