Pandian and Nellai had drastic changes once after getting converted as SF's pandian had 11 hours running time before getting converted as SF 6717/6718 used to be its number in MG and initial BG days .. the current 2637/2638 was used by erstwhile koodal Express which was once used to be reverse for vaigai .. pandian once after converted as SF it Traveling time was reduced to 9 hours and Nellai's Travelling Time used to be 13 hours and 30 minutes initial BG days , after Converted into SF its TT was reduced to 11 hours and 50 minutes