Replacing "R Series II" machines, the D8T, D9T and D10T track-type tractors meet Tier 3 emissions regulations with Cat's ACERT engines. The D8T is powered by a 347-hp C15 engine, the D9T by a 464-hp C18, and the D10T by a 646-hp C27. All three engines have an engine controller, which manages fuel delivery and airflow. Cabs are 8 inches wider and offer improved sight lines. A new Advisor Monitoring System provides on-board diagnostics to minimize downtime and maximize performance.