Early front u-joints

Well I yanked the drive shaft out tonight and disassembled it. It really didn't look to be inthat bad of condition. The boot is torn so the grease was mostly gone and the rest was all hard so after cleaninf and reassembly I thought it would make a difference. Nope. So Know what? Any suggestions as to what would cuase a strong vibration under acceleration? It smooths out at cruise... :banghead: