India clocked an impressive 3:27.77s amid cheers from a packed Jawaharlal Nehru Stadium.
The victory at Delhi accounts for second medal to Kaur, who ran the anchor leg. Her first Commonwealth Games medal came in Melbourne where she was part of 4x400m relay team, which won silver.
Ashwini, who erased a deficit of almost 10 metres in the third leg, modestly told a newspaper, "I gave it my best shot. We knew gold was possible and all of us were fired up."
Mandeep also credited Ashwini for the spurt for gold.