1986 Jeep Wagoneer 4X4 not working

I recently bought this jeep for a cheap vehicle to get to and from work. I knew the 4x4 wasn't working but was told it was a vacuum line. I found that the vacuum line going into the front axle wasn't connected correctly so when I connected it the 4x4 light came on but still no 4x4. I also noticed that when I drive in 1st and 2nd gear they are quite loud gears but as soon as I reach 3rd, 4th and 5th it is quiet. I am also having a hard time getting it into gear sometimes. I'm not sure if that would be a lubricating problem or something deeper. I also thought the vehicle had a limited slip differential but when I got stuck yeasterday when I thought the 4x4 worked the other rear tire didn't even try to kick in. I am at aloss and don't know where to start.I would appreciate any help. Thank you.