Driveshaft Slip Yoke
A splined sliding joint that allows the driveshaft to change length as the rear suspension moves up and down.
A driveshaft slip yoke is a splined metal component attached to one end of the driveshaft that slides into the transmission output shaft or transfer case. As a vehicle drives over bumps, the rear axle moves up and down, which changes the distance between the transmission and the rear differential. The slip yoke allows the driveshaft to adjust its length to accommodate this suspension travel.
The internal splines of the slip yoke slide along the external splines of the output shaft. A rubber seal (transmission tail housing seal) rides on the smooth outer surface of the slip yoke to prevent transmission fluid or transfer case fluid from leaking out.
If the splines on the slip yoke wear out or lose lubrication, they can bind, causing a distinct clunking or thumping noise when accelerating from a stop (known as slip-yoke bump). Regularly greasing the splines and replacing worn yokes prevents driveshaft vibration and transmission seal leaks.