ANSWERS: 1
  • Drive shafts are used to connect the motive power in most front-engine, rear-wheel-drive vehicles, including cars and trucks. They are also used to connect transfer cases to front-drive axles in most four-wheel drive trucks and cars with front engines. The vast majority of drive shafts consist of a sliding yoke, two universal or constant velocity joints, and a drive shaft tube or solid shaft defining most of their length. Removing them is not difficult, but several precautions should be taken while doing drive shaft work to keep them trouble-free.

    Operation

    Classic fore-aft drive shafts in front-engine, rear-drive cars and trucks connect the rear of the transmission to the pinion shaft of the rear-drive axle. They are typically between 4- and 6-feet long. Most fore-aft drive shafts spin at a velocity about three times greater than the drive wheels due to the final drive axle ratio. In top gear they may spin at the same rotational velocity as the engine or even greater in overdrive. Therefore balance and observance of key drive shaft angles is essential to maintaining a vibration-free, long-lasting drive line. Correct drive shaft geometry determines that the universal joints must continually operate through the exact same angle despite any up-and-down excursions of the rear axle due to weight or bumps.

    Drive Shaft Components

    In the front is a sliding yoke that has an internal spline that fits over the splined transmission output shaft. The yoke retains one-half of the front universal joint cross. The other half of the cross is held by the drive shaft tube, whose yoke is 90 degrees out of phase with the front yoke. At the rear of the tube is another yoke holding one-half of the rear universal joint cross. The two tube yokes by necessity have exactly the same rotational orientation. The other half of the rear universal joint cross is held by the pinion yoke, which is splined and bolted to the rear pinion shaft. The reason the front yoke uses a sliding spline is that, as the rear axle goes up and down over bumps, the rear axle suspension geometry dictates that the shaft must shorten as the wheels move up closer to the vehicle frame. The sliding spline allows this constant lengthening-shortening to take place while transmitting driving forces.

    Disconnecting the Drive Shaft

    Two different methods are used to connect the rear of the driveshaft to the rear axle. The first is the yoke-and-U-bolt method, where the two bearing cups of the rear universal joint fit into the pinion yoke arms where they are held by two U-shaped bolts with locking nuts. The other is a round drive flange behind the rear universal joint held to the pinion shaft flange by four bolts and two alignment notches. In any case, exactly mark the shaft and rear pinion positions before unbolting, so that the driveline will reassemble exactly the same way. Remove the nuts and bolts, maintain lock-washers, and push the shaft forward slightly to disengage the rear connection. Then carefully slide the shaft back and out of the transmission. Make sure no oil is leaking out of the transmission. If it is, you may want to temporarily clamp the flat part of a plastic bag over the rear transmission opening with a large hose clamp. The driveshaft is now ready for inspection and repair.

    Source:

    Driveshaftspecialist.com: Drive Shaft Types

    Driveshaftspecialist.com: Pinion Yokes

    More Information:

    A1driveshaft.com: Drive Line Type Reference

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