and only when I ride no hands...and only going over rough surfaces. it sounds like a rattling sound

. I just recently overhauled the drive train, so it's not that. it sounds like it's something in the front of the bike from what I can tell. My headset felt fine, but I adjusted/tightened it a little bit to make sure that that wasn't it. When I stand next to the bike, pick up, and drop the front end of the bike on the ground, I don't hear the rattling sound. When I'm riding with my weight forward and/or hands on the handlebars, there is no problem, but as soon as I sit up, it sounds like rattling coming from the front as the front wheel hits rough surfaces

it isn't the hub or a loose quick release either...

what could it be? I'm really hoping that it has nothing to do with the frame(reynolds 501 cromoly peugeot ), but I don't see any cracks or anything. I didn't think steel cracked easily tho. could it be something with either of the bearing races?

anyone ever experience this or might know what's going on?