ticking noise from 01 z71

[cstm68]

a few weeks or so ago my 01 silverado with a 5.3l started to make a weird ticking noise, it only does it at speeds above 50 or so and i can only here it when passing a wall or concrete barrier on the freeway with the window down. rpm does not seem to change the noise but speed does. has anyone had this problem. i dont think its the motor but worried it could be from the tranny, its got aboyt 125k on it.