The M18 Hellcat was an American tank destroyer during World War II. Armed with a 76-mm cannon, it was the fastest tracked armored fighting vehicle during World War II with a top speed up to sixty mph. As a result, Buick nicknamed it the Hellcat. The fast speed was reached by keeping armor thickness to a minimum. Hellcat crews took advantage of the vehicle's speed to minimize the enemy's ability to pierce its thin armor. The M18's new design incorporated several innovative maintenance features. The Wright R-975 engine was mounted on steel rollers, allowing maintenance crews to disconnect it easily from the transmission, roll it out onto the lowered engine rear cover, service it, and then reconnect it again. The transmission could also easily be removed and rolled out onto a front deck plate to enable quick inspection and repairs. The M18 carried a five man crew as well as forty five rounds of main gun ammunition, and an M2 Browning machine gun on a flexible ring mount for use against aircraft and infantry. The only M18 variant which was produced in significant numbers was the M39 Armored Utility Vehicle, a turretless model used to transport personnel or cargo. Also, it could be used as a gun tractor. This version was armed with a single M2 machine gun on a flexible mount. Created in 1945, this technical manual reveals a great deal about the Hellcat's design and capabilities. Intended as a manual for those charged with operation and maintenance, it details many aspects of its engine, cooling, turret and other systems. Originally labeled restricted, this manual was declassified long ago and is here reprinted in book form. Care has been taken to preserve the integrity of the text.