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I noticed that there was oil that was seeping out of where the axle bolts to the housing in the rear


From where the 4 nuts attach the backing plate??
If from here, your axle seals are probably toast. It's a good idea to replace those whenever you pull an axle shaft from the rear. Especially if your not careful while removing the axle's to swap the diff.

85 4Runner - With NEW Marlin 4.7 Gears!! It's a whole new beast!