Caterpillar dans l'ordre chronologique

The 973 was equipped with a 3306 Turbocharged diesel engine capable of producing 210 HP @ 2200 RPM. With a hydrostatic drive, the operator had ultimate control of their speed up to the top speed of 6.4 MPH in either forward or reverse.

After a testing period, the 615 was introduced in 1981, powered by a 250 horsepower Caterpillar 3306TA six-cylinder diesel.

The model was succeded by D9N.