Chevy Astro problems...PLEASE Help!!!?

i have 2 questions. 1st is every time i put my van in gear it makes a clink or clunk sound no matter if it's reverse or drive and 2nd question. it vibrates when i go down the road at 45 mph but it's smooth before it goes up to 45 and then when i let off the gas just give it a little gas it really viberates what would make it do that...thanks for e1's help