Hello and welcome to Just answer,
The pinion shaft inside the rear differential that the yoke attaches to has a collapsible spacer "crush sleeve" between the front and rear bearings on the shaft, if the nut on the yoke is over tightened the rear differential will need to be disassembled and the crush sleeve replaced, so the utmost care needs to be taken so this does not happen.
I don't mean to scare you here, this is not that difficult of a job but you will need a few tools as listed below in the instructions, some of these can be loaned from a local parts stores. Make sure you mark everything before you take it apart.
Drive Pinion Flange/Yoke and/or Oil Seal Replacement
Important: Observe and mark the positions of all the driveline components relative to the propeller shaft and the axles prior to disassembly. These components include the propeller shafts, drive axles, pinion flanges, output shafts, etc. Assemble all the components in the exact places in which you removed the parts. Follow any specifications, torque values, and measurements made prior to disassembly.
Use a container in order to retrieve the lubricant.
Important: Do not damage the axle housing sealing surface.
Important: When replacing the pinion oil seal and/or the pinion flange/yoke, observe the following guidelines:
Important: Install the pinion gear flange/yoke to the pinion gear shaft in the same position as marked during removal in order to maintain correct driveline balance.
Align the marks made during removal.
Notice: Do not hammer the pinion flange/yoke onto the pinion shaft. Pinion components may be damaged if the pinion flange/yoke is hammered onto the pinion shaft.
Notice: Refer to Fastener Notice in the Preface section.
Important: If the rotating torque is exceeded, the pinion will have to be removed and a new collapsible spacer installed.
Tighten Tighten the nut until the pinion end play is removed. Rotate the pinion while tightening the nut to seat the bearings.
Tighten Tighten the nut in small increments, as needed, until the rotating torque is 0.40-0.57 N·m (3-5 lb in) greater than the rotating torque recorded during removal.