SAD_1969_UTM_Zone_23S to WGS84 Coordinate convertion using ArcGis Desktop problem

Dear All,

I have shape data having projection SAD_1969_UTM_Zone_23S(Brazil) coordinate system. I had successfully converted SAD69 coordinate to WGS84 Coordinatesystem by using caluculate geometry option in arcgis.

Below is the tutorial url which i have used as reference to the convertion

http://www.youtube.com/watch?v=ewUcbsnQSuI


but the problem is the location of converted WGS84 coordinates are deviated from correct location in map.

Can anyone help me to come out of this situation.

Thanks in advance


Thanks & Regards,
Subbarao