automatic transaxle on 2001 Hyundai Santa Fe

HI have a problem automatic transaxle is not change speed when is needed sometime does and sometimes dont why?

Asked by for the 2001 Hyundai Santa Fe
You'll need to get it checked out to know why it's having a problem. There are too many possibilities and it's impossible to diagnose without seeing and driving the vehicle.
The shop should check to make sure the transmission control module has the latest software from Hyundai, and check for and diagnose any trouble codes stored in the module.