93 geo auto trans no sec gear when warm

93 geo 3cyl auto trans works fine when cold, sec gear becomes same as neutral when warm, no burnt fluid jus changed no metal shavings in fluid or filt low, drive and rev all work fine all the time need help PLEASE

Need more details to suggest something. Does it go from first to second and then lose drive in "D" or is "D" working fine and the problem is in "2" only. Do you have second when you manually move the shift lever to "2".

sounds like a trashed band in the transmission to me.