95 Sierra 3500 4x4 problems

I have a 95 sierra 3500. It has a 5.7 tbi with a 5 speed manual tranny but first is actually refered to as low gear for my tranny according to my truck manual. Anyway recently when I shifted into 4hi everything seemed to engage fine but I have a pretty loud whine while driving that sounds like its coming from my front diff. Also I'm not sure how its supposed to feel when engaged in 4hi but its a signifigance differance as far as it feels like theres alot of resistance when accelerating and slowing down. Similar to how 4lo feels but its not in 4lo as I can still drive normal speeds. If anyone has any ideas I would appreciate it. Ive finally made the switch from driving a car and I'm not real familiar with 4x4 drivetrains. So any suggestions would be greatly appreciated. Im also posting another thread regarding another issue for the same truck so please check it out also.