Synthesis of large-pore zeolite [Al]-SSZ-31 has been studied by dry-gel conversion method using 1,8-diazoniaoctane type of structure-directing agent. Pure SSZ-31 was obtained with NaOH/SiO2 = 0.05-0.12, while the product was contaminated with MFI below or above this range. Snowtex-40 (colloidal), as the silica source yielded SSZ-31, while Cab-O-Sil M-5 and Ludox AS-40 yielded mostly MFI phase. A phase change: BEA-->SSZ-31-->MFI was observed with time course at optimum NaOH/SiO2.