Grinding noise from front differential

I recently purchased the vehicle listed above and the differential has recently started to groan, and the vehicle would feel like it does not want to move when turning far to the left with 4x4 off. It does do the same turning in both directions and more severely with 4x4 high on. I purchased it from a family member, and they said it only did that with 4x4 activated and I asked when it had its fluid changed and they said never in the car's life. I quickly changed the fluid, but the problems remains. I am just wondering what exactly could be causing this or if I will have to replace the whole differential? Thanks.