Buick Encore: Description and operation

PROPELLER SHAFT DESCRIPTION AND OPERATION

The function of the propeller shaft is to transfer power from the transfer case to the differential clutch. It consists of three pipe sections, a front Rzeppa joint, two Polhem joints in the center and a rear Rzeppa joint. The propeller shaft's support bearings are fitted by the Polhem joints. The bearings are mounted in rubber bushings which are fitted in brackets, and these in turn are bolted to the underside of the vehicle. The position of the brackets is very precisely measured during vehicle manufacture. The propeller shaft does not run in a straight line between the transfer case and the differential clutch but is instead gently curved, and this is to avoid vibration.

Front Drive Shaft

The propeller shaft connects into the transfer case pinion with a splines equipped pin which is part of the front drive shaft universal joint. The function of the joint is to handle the difference in angle between pinion and propeller shaft, as well as to be flexible longitudinally.

Support Bearings

Directly after the Polhem joints are the propeller shaft's support bearings, which are the single-row, permanently-lubricated groove ball bearing type. They are fitted in rubber bushings which in turn are fitted in brackets.

The brackets are bolted to the underside of the vehicle and their position is very precisely measured during vehicle manufacture. If the support bearing brackets are fitted incorrectly then vibration will occur.

Rear Drive Shaft

The propeller shaft connects to the differential clutch driver by means of the rear drive shaft universal joint which is bolted to the driver.

The function of the joint is to handle the difference in angle between differential clutch driver and propeller shaft, as well as to be flexible longitudinally. The rear drive shaft universal joint is also a Rzeppa joint and is friction welded to the rear pipe section and constitutes one unit together with the propeller shaft.

Front/Rear Drive Shaft Universal Joint (Rzeppa Joint)

The Rzeppa joint consists of an outer bearing race, which also constitutes the joint's housing. On its inside are 6 semi-spherical grooves. The inner bearing race consists of a cylindrical section, in the periphery of which are 6 semi-spherical grooves. The inner bearing race is fitted inside the outer one and there are 6 steel balls between the grooves. A ball holder is fitted between the outer and inner bearing races. There are steel balls between the bearing races which transfer the movement between outer and inner bearing races.

Center Joints (Polhem Joint)

There are Polhem joints fitted between front and center pipe sections as well as between center and rear pipe sections. Their function is to handle the angle difference between pipe sections. The joints are angled 45 degrees in relation to each other to avoid vibration.

The Polhem joint consists of two forks, produced in forged steel which grip a cross by means of arms. The pins of the cross are mounted in needle bearings in the forks' bearing sleeves. The sleeves are permanently locked in the forks by means of compressive strain.

The bearing sleeves are permanently lubricated with synthetic special grease which contains molybdenum disulphide.

The drive shaft universal joint is friction welded to the relevant pipe section and constitutes one unit together with the propeller shaft.

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