This training manual, the first of two volumes, comprises the first six blocks in a nine-block in-service training course for apprentices working in heavy duty mechanics. Addressed in the individual blocks included in this volume are the following topics: shop equipment and practices; procedures for starting, moving, and stopping equipment; the principles and theory of hydraulics; brakes; power trains; and frames, suspensions, running gear, and working attachments (bearings and seals; track machine undercarriages; track machine final drives; track machine steering; wheel machine suspensions; tires, rims, and wheels; wheel machine final drives; wheel machine steering and front suspension; and working attachments). Each block contains a section on parts theory that gives the purpose, topics, operations, and applications of the parts and systems being discussed; a set of questions on parts theory; a section on scheduled maintenance and service repair; a set of questions on service; and a list of validated tasks to be completed during the course of daily on-the-job routines. The manual is illustrated with photographs and drawings. (MN)