When I step on the gas, there is a klunking noise.

Sounds like a broken motor mount?

is it 4x4 front cv axle bad

Universal joint, perhaps? Could be a few different things, as stated in previous answers. A hands on diagnosis is probably in order.

this is mr. motor-mouth i had this promblem before and the problem was my fuel fiter change that and your truck should pick up speed a fuel fiter has trash in it and slows your truck down the cost is around 10-15 dollars