A torque tube system is a power transmission and braking technology that involves a stationary housing around the drive shaft, often used in automobiles with a front engine and rear drive. The torque tube consists of a large diameter stationary housing between the transmission and rear end that fully encloses a rotating tubular steel or small-diameter solid drive shaft (known colloquially in the U.S. as a "rope drive") that transmits the power of the engine to a regular or limited-slip differential. The purpose of a torque tube is to hold the rear end in place during acceleration and braking. Otherwise, the axle housing would suffer axle wrap, such that the front of the differential would lift up excessively during acceleration and sink down during braking. Its use is not as widespread in modern automobiles as is the Hotchkiss drive, which holds the rear end in place and prevents it from flipping up or down, during acceleration and braking, by anchoring the axle housings to the leaf springs using spring perches. Construction The "torque" that is referred to in the name is not that of the driveshaft, along the axis of the car, but that applied by the wheels. The engineering problem that the torque tube solves is how to get the traction forces generated by the wheels to the car frame. The torque moving the wheels and axles in a forward direction is met with an "equal and opposite" reaction of the axle housing and differential, making the differential want to spin in a reverse direction, in the same way that a cyclist "pops a wheelie", lifting the bicycle in the air in the opposite direction from the turn of the wheel. The essential problem is how to keep the differential from rotating during acceleration and braking. The torque tube solves that problem by coupling the differential housing to the transmission housing and therefore propels the car forward by pushing up on the engine/transmission and then through the engine mounts to the car frame, with the reverse happening during braking. In contrast, the Hotchkiss drive transmits the traction forces to the car frame by using suspension components such as leaf springs or trailing arms. A type of ball and socket joint called a "torque ball" is used at one end of the torque tube to allow relative motion between the axle and transmission due to suspension travel. Later American Motors