Trailer clunking??

Just experienced this myself. Likely the preassure cylinder that inside the hitch mechanism. If you can move the female portion of the hitch by hand, you might want to purchase a new unit from Bass Cat. Really simple to change out and install.

Its not uncommon for the ball mount (male part of the hitch) to move in the receiver. Theres usually a bit of slack. Thats probably what youre hearing when you accelerate. Every trailer Ive had will do that sometimes, especially if youve had to come to a faster than normal stop right before you accelerate.