engine has full power start going up hill losses speed

What is your question?

when driving on flat road can get up to 60 fine start up hill losses speed and can't get it back up to speed won't shift gear no codes except ignition coil o2 sencor code has been on for a long time this problem just started 4 days ago changed transmission fluid and filter

What makes this problem better or worse?

ok on flat ground starts and gets worse going on a incline or uphill

How long has your 2007 Nissan Frontier had this problem?

4 days