I purchased a stock diff with a 4.77 gearset installed. When spinning the input shaft, both output shafts spin smoothly. However when I spin the output shafts in opposite directions, it has spots that take some extra force to push past. Is this normal due to the LSD or is there and internal issue? I cannot see any damage to the spider gears.

 

I had the same problem in my car and replacing the LSD unit fixed it. Most likely it is binding internally. In my personal case, the car would make clunking and popping sounds at low speed and full lock situations such as maneuvering for parking.