My birfs are leaking grease. Not too bad, but it has accumulated enough to where the u-bolts are completely covered. I was told this happens when the inner seals go bad? What will happen if this is let go for too long? It's not actually my truck, but one I quite possibly may be buying, and wanted to use it as a bargaining tool and also good to know. What all do I need to replace this (as far as parts are concerned), just inner seals? Thx in advance. BTW, the truck is an '85 pickup with 150k on it.