At about 60-80kph, when it is about to shift to fourth gear, the gears slip and the rpm just revs at hindi na nag-shift.

what should i do with this?

a mechanic told me that it is stuck to third gear na.........how about your opinion guys?

he's talking about........kung kaya daw dukutin yung sa automatic yun muna bago replace tranny. i don't get what he was saying. BTW my car is galant ss at.