U Joint

u joint

Universal joints allow drive shafts to move up and down with the suspension while the shaft is moving so power can be transmitted when the drive shaft isn't in a straight line between the transmission and drive wheels. Rear-wheel-drive vehicles have universal joints (or U-joints) at both ends of the drive shaft.

A propeller shaft, or propshaft, connects the rear axle to the gearbox on front-engined rear-wheel-drive cars. At each end of the propshaft there is a universal joint (UJ), which allows the rear axle to move up and down in relation to the gearbox without bending or snapping the shaft.