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.