Transmissions and transfer cases are connected to axles using driveshafts, and those connections use U-joints and yokes. While the typical wear item in these links are the U-joints, there are times when yokes can give you problems as well. You may need to swap a yoke to one that supports a different-sized U-joint or when excessive U-joint angles are in play yokes may wear or become damaged. Transfer case or pinion yoke seals can start to leak over time and warrant replacement.
Yokes on the transfer case can usually be easily removed and replaced, retorquing the nut to factory specs. However, when it comes to axle pinion yokes, life can get a bit more complicated. The pinion gear spins on a pair of tapered roller bearings in the axlehousing or in the third member of an axle. During initial installation of the pinion with new bearings the installer preloads the bearing stack with a bit of tension. As the new bearings break in, that slight preload will diminish and leave the bearings free to spin but with no end-to-end play in the stack. If no preload were used, the bearings would end up with slight play in the assembly.
When installing the pinion, there are two ways to set the bearing preload. In one instance, a nonreusable crush sleeve is collapsed between the bearings when the assembly is tightened by the pinion nut, and this sleeve provides the bearing preload tension. The second method uses a solid cast-iron spacer, which does not collapse, so shims next to the spacer are added and subtracted to accurately set the bearing preload.
To remove and replace a pinion yoke and/or seal on an axle with a solid spacer, you can simply remove the pinion nut and then reinstall everything with a new pinion nut, tightening it to the proper torque spec. However, you can't really do this on an axle that uses a crush sleeve in the pinion bearings as you cannot reliably gauge the pinion bearing preload with a new yoke or nut.
We have seen cases where the pinion nut and yoke were removed to replace a pinion seal on an axle with a crush sleeve. The same yoke was then reinstalled and the same pinion nut reused, and tightened back to its exact original position. In these cases, the pinion nut was tack-welded to the end of the pinion to reliably retain it. This can be used when you'd really like to avoid tearing into the axle and you'll risk a quicker, cheaper fix.