TRANSMISSION PROBLEM on 2005 Kia Amanti

I PURCHASED A 2005 KIA AMANTI 3.5L V-6 WITH A 5 SPEED AUTOMATIC TRANSMISSION. THE TRANSMISSION SHIFTS SMOOTHLY BUT DOES NOT EVER SEEM TO SHIFT INTO 5TH GEAR WHICH IS SUPPOSED TO BE OVERDRIVE. DEFINATELY SHIFTS INTO 4TH GEAR. I CAN NOT EVEN GET TO 5TH GEAR WHEN DOING A MANUAL SHIFT. THIS IS CAUSING POOR GAS MILEAGE BECAUSE ENGINE REVOLUTIONS ARE HIGH WHEN TRAVELING DOWN THE FREEWAY AT 65-70MI/HR. I DO NOT HAVE THE ENGINE MALFUNCTION LAMP ON BUT NOTICED THAT THERE WAS SUPPOSED TO BE TRANSMISSION CONTROLLER SOFTWARE UPDATE FOR THIS 2005 YEAR AMANTI. I PURCHASED THE CAR USED. IT WAS A HERTZ LEASED VEHICLE FOR 4 YEARS AND MAY NOT HAVE RECEIVED THE LATEST UP DATES. THE CAR WENT ON THE AUCTION BLOCK JANUARY OF 2010 AND I PURCHASED IT IN DECEMBER OF 2010. I AM ACCORDING TO CAR FAX THE 4TH OWNER OF THIS CAR. 2 PREVIOUS OWNERS WERE USED CAR DEALERS.

2 answers
would advise taking this to your local KIA dealer. like a
lot of cars today, KIA does not have a specific mileage to service the transmission. it is a KIA specific fluid.
would also see if there is a software update. most KIA's
are not well maintained; most people just drive 'em until
they drop, especially if they are leased.
Did you get this problem solved? I am having the same problem and put in another transmission and it is still doing it.