97 sunfire auto transmission shift problem

My 1997 2.2L 3 speed automatic transmission has recently started to shift very late. from 1st to 2nd 40km or 4000 rpm and from 2nd to 3rd 80km. I have replace the filter and fluid to no avail and the oil didn't have much particles in it. Please Help

I can't offer any help but I have a question.

I just bought a 99 sunfire and want to change the tranny fluid and filter. Is there a drain plug in the torque converter?

Any other info?