2005 chevy astro van tranmission?

hi i had 2005 chevy astro panger van and i just sold it this week and the person who i sold it to he says it has tranmission problem. when i had the van there was no problems i ran great,it was a fleet van so all service was done on time. is it the tranmission or it's something elso that efecting the tranmission operations. please give all answers,thank you