Six unique mainframes are manufactured to give J-Series crawler dozers perfect balance, regardless of blade or track configuration, says John Deere. Completely redesigned, the models have longer track frames and improved balance for better grading. An advanced monitor displays machine operating parameters and acts as an interface for the operator to change operating characteristics of the machine, read diagnostic codes, and troubleshoot systems from the seat. Model 750J and 850J use PowerTech engines ranging from 145 to 200 horsepower. Estimated list price: $280,000 to $350,000.