Overdrive
 

Hello to everyone.
I recently bought a 1988 Volvo 240 DL with a 2.3L non turbo and a automatic transmission. I have never owned a volvo before so I am completely oblivious when it comes to these cars. I saw that there is an overdrive button on the shift lever but I accelerated gradually up to about 60mph and only counted 3 gears and it seemed like the rpm were kinda high. Is this tranny supposed to have a 4th gear? Because I pressed the button on the shift lever about 5 times but nothing happened. And if it does have a 4th gear how can I get the overdrive to work? Any help would be greatly appreciated.