We compute the spectral densities of $T^{mu u}$ and $J^{mu}$ in high temperature QCD plasmas at small frequency and momentum,, $omega,k sim g^4 T$. The leading log Boltzmann equation is reformulated as a Fokker Planck equation with non-trivial bounda
ry conditions, and the resulting partial differential equation is solved numerically in momentum space. The spectral densities of the current, shear, sound, and bulk channels exhibit a smooth transition from free streaming quasi-particles to ideal hydrodynamics. This transition is analyzed with conformal and non-conformal second order hydrodynamics, and a second order diffusion equation. We determine all of the second order transport coefficients which characterize the linear response in the hydrodynamic regime.
