I think it's the drive shaft.. but I'm not sure. when I let of the gas going down the road it clanks and the faster I go the faster it clanks. It doesn't make a sound when I apply throttle or brake but it starts to vibrate the faster I go. The sound gradually became worse after towing an s10 on a car dolly. Need help!

 

Moving this to 2nd Gen for you.

 

Try shaking the rear drive shaft around and see if your u joints are loose. If not try jacking up the axle and try and lift the tires up and down. Does the truck vibrate when it clanks?

 

Yes it starts to vibrate after getting up to around 30

 

Try moving the drive shaft from under it as well as the tires but if it starts at 30... How long have you had these tires and how many miles on them? Ever changed the shocks? Try moving the shocks by hand as well. Front and rear. My front shocks took a dumb and would rattle around