For pt.I see ibid., vol.11, p.4187 (1978). Effects of tunnelling rotation of ND4+ ions on 2H-NMR lines are analysed. Detailed lineshape calculations are supplied. All terms in the quadrupolar Hamiltonian and secular dipolar interaction between deuterons are taken into account. Asymmetry and level crossing are characteristic features observed in the lineshapes. The latter effect makes measurement of the tunnelling frequency possible. Sets of theoretical lineshapes are presented showing their evolution with tunnelling splitting and with magnetic field. The main conclusion is that complete interpretation of a given ammonium compound (ground torsional level structure and tunnelling splitting value) requires measurement of the field dependence of the 2H-NMR lineshape.