Can you get a pic up? I assume you are talking about the splined slider that goes in to the transfer case for the front prop? There is an oil seal at the front where the splined end goes in. The UJ will not have any grease or oil to speak of as it is just an open part on the Propshaft. There shouldn't be much more than a copper slip amount of grease on the splines. I cannot think of anywhere else where the oil could come from other than that oil seal.