What nickname is commonly used for a non-synchronous manual transmission?

A non-synchronous manual transmission is commonly nicknamed a crash gearbox. Its gears lack synchronizing mechanisms, so the driver must match transmission input and output speeds before engaging another ratio.

The nickname refers to the grinding or crashing noise that can occur when an incompatible gear is forced into engagement. Older designs used sliding gears or constant-mesh gears with dog clutches, but neither arrangement automatically equalized shaft speeds in the way a modern synchromesh gearbox does.

Before synchronizers became widespread, drivers learned techniques such as double-clutching and careful engine-speed matching. Non-synchronous transmissions are still used where durability, simplicity, and high torque matter more than effortless shifting. Examples include heavy trucks, tractors, industrial machinery, power take-offs, and some racing or motorcycle applications.

“Crash gearbox” does not mean a transmission that has been damaged in a crash. It is an established informal name for the transmission type. “Powertrain” is the broader system containing the engine and drivetrain, while “Tiptronic” describes a manual-selection feature associated with certain automatic transmissions. “Slushbox” is informal slang for an automatic transmission, not a non-synchronous manual.