FORD EXPLORER TRANSMISSION NOT SHIFTING

My 1999 Ford Explorer Suddenly Had Transmission Problems. The Trans Wont Shift Down To 1st At A Stop Normally And The Upshift Usually...

I Have No 1-2 Shift In The Transmission Automatically. It Will Shift If You Start Off In 1 And Increase Rpms To Around 3000 Then Let Up On...

I Bought This A Year Ago And The Overdrive Light Came On. So, I Had The Transmission Serviced And A Faulty Position Sensor Replaced On It....