4wd

RECENTLY I PUT A A YEAR NEWER 5 SPEED TRANSMISION/TRANSFER CASE IN MY 83 TERCEL SR5 4WD WAGON, (84).. HOW DO I CHANGE THE GEAR RATIO FOR THE 4 WD? IT CLOCKS IN AT 2500 rpm AT 5-10 MILES PER HOUR. COULD IT BE THE CHANGE OVER SELENOID? ANY THOUGHTS? IT GOES INTO 4 WD, BUT HAVE TO GO UNDER THE CAR TO RELEASE IT