8 3/4 grease leak .

Dana67Dart said
I would suspect, regardless of the seal location (but from OPs description I suspect pinion is location in question ) there are only a handful of reasons for a leak

  1. Seal surface is grooved or damaged is some way.
  2. the seal is installed incorrectly
  3. the seal is not correct for the application
The spline should never get oil to it if the seal is good.
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I disagree, many of the diffs i have had apart have sealant on the splines,a rubber waser/insert
Or a rubber coated washer that seals spline. Service manual will specify the method of sealing.