Bound-bound (2) Sigma(+)-(2) Sigma(+) and (2) Sigma(+)-(2) Pi interactions and their effect on the rotational-vibrational levels of Rydberg states of ArH/ArD have been investigated. Strong interactions have been obtained for the B (2) Pi-C (2) Sigma(+), D (2) Sigma(+)-E (2) Pi, and E (2) Pi-1 (2) Delta pairs of states in accord with recent experimental analyses of Rydberg spectra of ArD. Predissociation lifetimes of A (2) Sigma(+), C (2) Sigma(+), and D (2) Sigma(+) as well as transition energies and radiative lifetimes for Rydberg states up to 4f have been also calculated.