Rear End Noise

[Short Circuit]

I was on my way home in my 66 the other day and I was going up my driveway. I made it about half way up my driveway and the rear end started making a noise. It sounded a lot like a baseball card in a bycicle spoke....just louder. I stopped the truck and backed it up and pulled forward a few times and the noise stopped. Do any of you guys know what it could have been? I am thinking a rock got stuck in something...I have a 1/4 mile gravel driveway. I hope that's what it was anyway. I have not drove the truck since then, nor have I got under it to investigate....haven't had time to do either. Do yall think it was anything to worry about?