4×4 not working properly

I have posted about this a while ago. The problem is when I put it in 4×4 the front end immediately starts to drag and starts to make a "whining" sound and is also very hard to steer. I know it’s harder to steer since all wheels are turning but it’s virtually impossible and if I need to make a hard turn I can’t unless someone else would be pushing also. When in 2×4 their is no noise or drag or hard steering whatsoever. I have tried synthetic gear oil. I used mobil1 75w-90 for hypoid gears. When I changed it I had no metal shavings either. Is their anything I need to check or replace? I just want to fix it and have a working 4×4!!! Thanks in advance for any help.