pull your front driveshaft and run it. if your worried about it unloading to the front just wire a shaft(allen wrench, anything) through the front cup to hold it stationary. do a couple high grip passes and see if the tickings gone. don't run much its hard on the center diff, but fine for a couple passes. that'll get you 50% diagnosed......
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It's "Dr. _paralyzed_" actually. Not like with a PhD, but Doctor like in Dr. Pepper.