Drive/Propeller Shaft: Description and Operation

Torque is transmitted from the transmission to the axle through a propeller shaft and the universal joint. The propeller shafts vary with the vehicle's wheel base, transmission and rear axle combination. Propeller shafts have universal joints at each end in order to accommodate angle variations of position between the transmission and rear axle caused by suspension motion. The driveline connects to the transmission with a splined slip joint and to the axle with either a strapped flange or a piloted flange.

The driveline components in this vehicle are balanced. Balancing provides a smoother running driveline operation. These components include the propeller shaft, rear axle, engine and transmission. All components must be reassembled in the exact relationship to each other as they were when removed.





Phasing
The propeller shaft has yoke lugs (ears) in line with each other. The design with yoke lugs in line with each other is called phasing.

A phasing design reduces the vibration in the driveline. Vibration in the driveline results from the way the universal joints move in order to accommodate the angle between the engine and the rear axle.





The smoothest driveline results when the propeller shaft (2) is in phase. Small fluctuations in torque due to the changing angles occur at each universal joint as the propeller shaft rotates.





The propeller shaft is in phase when the two ends of the propeller shaft experience the same torque fluctuations. As the torque increases at one end it also increases at the other. The periodic torque increase produces smooth rotational velocity fluctuations and minimizes the jerk which would occur with opposing torque changes at each end.

A one-piece propeller shaft will always be in phase unless it was built incorrectly. If the one-piece is incorrectly built, you must replace the propeller shaft.

Do not reweld the propeller shaft under any circumstances. A two-piece propeller shaft goes out of phase if taken apart at the center slip yoke and reassembled incorrectly. If the two-piece propeller shaft has been taken apart it can be put back in phase; however you must take caution. There are two ways that you can put the propeller shaft back into phase but only one way that it will be in balance. Refer to Correcting Driveline Vibration RWD and 4WD in Vibration Diagnosis and Correction under Steering and Suspension Testing and Inspection. As with the one-piece propeller shaft, under no circumstance should you reweld the two-piece propeller shaft.

Balancing
You must reference mark the propeller shaft and rear axle before removal or separation in order to ensure that upon reinstallation, the propeller shaft is in phase, balanced, and aligned with the axle correctly.

The front and rear shafts of a two-piece propeller shaft are a balanced matched set. Severe damage to the driveline may result if the parts of the propeller shafts are inter changed and installed without re-balancing the interchanged parts. The label on the two-piece propeller shaft which also states this critical warning should not be removed.





The one-piece propeller shaft has an orange arrow on the identification label (1) which indicates the low point of the small residual imbalance that still remains after balancing the shaft within its specified tolerance.





The two-piece propeller shaft has an orange dot on or near the pinion flange which indicates the low point of imbalance (2). However this dot may be faded, and you must reference mark the relationship of the components before removal.

An orange dot also is on or near the pinion flange of the rear axle. The pinion flange of the rear axle may also have a stamped X at the same location which indicates the high point of residual imbalance. You must align the orange arrow or dot on the propeller shaft as closely as possible with the orange dot or X on the rear axle in order to offset the residual imbalances and produce the smoothest possible driveline.