You can get many good colleges for Post Graduate after M.Tech in Mechanical Engineering in India.

Like IIT Bombay

IIT Delhi

IIT Kharagpur

IIT Kanpur

IIT Madras

IIT Mandi

IIT Guwahati

IIT Ropar

IIT BHU

NIT Tricky

NIT Warangal

NIT Suratkhal

IIEST Shibpur is good

NIT Durgapur

NIT Raipur

NIT Srinagar

NIT Rourkela

NIT Surat

NIT Bhopal

Jadavpur University

JNU

Delhi Technological University

PMES,UP

And last but not the least

ICT,Mumbai.

Hope this answer helps.

Best of luck for future endeavours.