My neighbour's datsun 120y 1978 model transmission still ok & never done anything. i only know about proton's gearbox problems lah......like when running suddenly the gear automatically shifts to neutral....when this happen frequently then its an indication that the gearbox is gonna "kong" & normally a 2nd hand g/box from potong kereta wil b used as replacement.F1turbo said:Does anybody know when its time to rebuild your manual transmission ? is there a "time" when you know you have to do it?