2004 Drive Train Problem

[2004XLT]

I've been noticing a strange vibration at low to high speeds which has been getting increasingly more pronounced. My road is on a steep hill, leaving my driveway the expy feels normal, but coasting down the hill about 30ft I notice what I think is torque converter lockup (has always done this at the same point after pulling out of the driveway), then the vibration starts. This is at about 15MPH. It doesn't feel like a wheel out of balance, more like driving on gravel. Also along with this problem I've experienced slower acceleration, some "drag" when coasting, worse gas mileage, and if I switch from 2H to A4WD on dry pavement then I get a loud bang, however the sound is not 4WD engaging because I don't feel it binding. This has never happened before. It's my understanding that A4WD will engage 4WD only when there is slipping detected. The vibration carries through all gears and speeds, but sometimes the exp feels completely normal, acceleration and ride quality being fine. This makes me think my problem is in the 4WD system and not transmission. It may also be worth adding that my U-joints are starting to go. I'm looking for any suggestions on diagnosing this issue. Thanks