Scratching noise at initial acceleration?

Hey everyone. Recently I noticed a weird scratching (almost rattling) sound right when I accelerate that lasts for about a second or two and then goes away. I haven't really gotten a chance/noticed it when I'm already moving, but it's definitely there from a stop. Only happens when in drive or reverse or at least isn't noticeable enough in neutral. I've read a little and some people mentioned exhaust bits, but I'm not sure if it would make sense seeing as it only happens in drive/reverse. Others have mentioned u joints. I haven't been as good recently about greasing my u joints and I have taken it through some water deep enough to submerge the driveshafts. Also hit a pretty deep rut this past weekend a little faster than I should have...possibly f*d up some suspension bits? I'll crawl back under later tonight and start checking what I can. Any insight is appreciated!

4.0 v6 w/ about 60000 miles.