ZF input shaft seal

Not hard at all. Remove the three small bolts holding the retainer on (5mm allen) Sometimes the seal can be a bit of a bitch to get out without scarring the housing but usually not too bad.Take your time!
Make sure the housing is clean before you install the new seal.If the seal isn't coated on the outside, put a coat of red Locktite on it . Also,make sure it goes in with the "lip" facing the correct way. Also a good idea to put a small amount of sealer on the housing where it meets the case.

Ron

As Ron said, sometimes its a bitch getting the old seal out. My undisturbed '72 ZF had the seal stuck in with epoxy-aluminum! But its a std seal available at any bearing supply house. The part number will be on it if you don't maul it too badly during removal. And the allens are half-height metrics that are usually very tight, so be sure you use a metric allen wrench, or you may rip the hex outa one or more screws with an SAE allen wrench.

There is an enhanced version of the Boss’s POCA article here http://www.panteraplace.com/page10.htm

Mike