Hello Aspirant
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Top colleges for mechanical engineering after diploma:
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Alliance university Bengaluru
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Manipal academy of higher education.
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Visvesvaraya technology university, belagavi.
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Acharya institute of technology, Bangalore.
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National institute of technology,tiruchirappalli
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Invertis university, Bareilly
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Go through official websites of this above colleges there you can found the brochures.
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I will provide the link below to know about the  other Colleges after diploma going to pursue mechanical engineering:
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https://www.careers360.com/colleges/government-engineering-college-sreekrishnapuram/btech-mechanical-engineering-lateral-entry-course.
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If you have any questions further let me know.
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Thank you!!!

Dear aspirant,
The top engineering colleges after diploma for mechanical engineering are
IIT Delhi
IIT Madras
IIT BOMBAY
IIT MADRAS
IIT KARGHAPUR
IIT KANPUR
BITS PILANI
BANARAS HINDHU UNIVERSITY
IIT GUWAHATHI
PSG COLLEGE OF TECHNOLOGY
SASTRA UNIVERSITY
BANGALORE INSTITUTE OF TECHNOLOGY
NIT TIRCHURAVALI
Hope my answer will help you
For any further queries drop a comment below
Thank you

Hi
Veermata Jijabai Technological Institute
IIT Gandhinagar - Indian Institute of Technology, Gandhinagar
Amity University
Lovely Professional University
International Institute of Management and Technical
Wisdom School of Management
CU - Chandigarh University
Thank you::)