Hi, USN

I'm shooting from the hip and going with a general proceedure on a typical seal replacement. Should be correct. Take the "U" joint bolts out and push the drive shaft foreword enough to drop the end of the drive shaft down and out of the way. Take some masking or electrical tape and go around all the "u" joint cups to keep the two that are not in the shaft from falling off. Remove the large nut on end of the pinion shaft and remove the yoke. Most of the time, the yoke will knock off with a small hammer, but sometimes you need a puller. Tale a pry bar and pry the seal from the housing. Sometimes you have to drive a screwdriver in the edge to pry it out. Best to take the old seal out and have it ready at the parts store to match up. Use non-hardening sealer on the outside edge and tap seal into the housing. Use wood block to tap seal into place if possible. Replace nut and torque to specs. Refer to a service manual or maybe someone on the forum knows the right torque for your make/model. Then hook up your "U" joint (now is the time to check it out and replace the joint if it is bad) and you're done. Grease it and the other joints if they have fittings.

Truck Tinker