don`t forget, if your passat runs inline engine it will have the torsen type 4wd basically same as the A4 Quattro, s4 rs6 and so on , which is perm 4wd but split 70-30 i think when slip is detected more goes to the rear, a3 and tt run haldex system which is electronic, as does the r32 and 2.8 v6 bora and golf, mk1 skoda octy and seat freetrack, rear diff only kicks in when the abs detects slip