The Allison T40, company designation Allison Model 500, was an early American turboprop engine composed of two Allison T38 power sections driving a contra-rotating propeller via a common gearbox.
The T-40 amphibious scout tank was an amphibious light tank used by the Soviet Union during World War II.
T40 is disability sport classification for disability athletics, specifically athletes of short stature.
The Rocket Launcher T40/M17 (Whizbang) (sometimes spelled WhizBang) was a tank-mounted multiple rocket launcher used by the United States Army during World War II.
The 3" Gun Motor Carriage T40, later given the production model number M9 was a US tank destroyer (a self-propelled gun designed for fighting tanks), of the early part of World War II.