With a worn double cardan CV joint in your drive train, every time the operator places the vehicle in drive gear to move forward, they will hear a banging sound. This occurs because of the gap in one or both of the U-joints that make up a double cardan CV joint. Just like a set of U-Joints, this driveshaft component will wear if not properly lubricated. If this drive component is allowed to break completely, the drive shaft will become disconnected and fall to the road which could actually flip the vehicle or it could come through the floor pan in the passenger compartment.
The double cardan CV joint is similar to the U-joints but has two sets of joints instead of just one. This drive component is located just aft of the transmission and is the connection from the transmission to the drive shaft to power the vehicle. The reason a double cardan CV joint is used instead of a U-joint is to provide for a greater angle from tranny to drive shaft. The most common application is when the rear differential is off set and a different angle than just straight back is required to connect the rear end to the power plant of the vehicle.
To replace a set of double cardan CV joint requires that the vehicle be lifted into the air for the greatest amount of access area to this drive train component. Just like a set of U-joints, the double cardan CV joint are taken off by removing the clip on the side of the joint. There is a clip at each junction so removal is easy. Once the U-joint is removed, the yoke must be inspected for damage and replaced if necessary.