My manual 4 cyl

My manual 4 cyl. AWD Sportage makes a rattling noise between 1600 and 1900 rpm, at any gear change. But if I engage the 4X4 lock, it does not do it. The dealer replaced the first and 2nd gears in trans. And the whole transfer case but nothing has changed. Still the same noise, could it be the front differencial trying to engage the AWD uncessfully, sounds like gears trying to engage!