Tie someone under the truck and go for a drive, they can maybe hear it better from under there
But seriously, it all depends on what speed the sound starts. If its as soon as you move just have someone walk beside the truck and see how that goes. grease the u-joints anyway and see if it goes away. If it does change them. You can also see if they are dry while doing that and check for extensive backlash (play).
Since its work under the truck and you probably dont have a grease gun and grease so you may as well just get it checked at a reliable shop. Have them show you the problem before they fix it and tell them you want the old parts back.