what is over drive
Hello 1991/96-- Overdrive usually is the highest gear on your transmission. It means when you are running at highway speeds (generally over 40 mph.) you will running at lower rpms. and you will therefore get better fuel efficiency. Your Celica has a switch that will allow you to block out this highest gear. Usually you will always want it on in normal conditions. A time when you might prefer turning it off would be in mountainous terrain. A good link to a very good general primer on transmissions can be found at http://www.samarins.com/maintenance/transmain.html. Good luck from Bovan.
Search Toyota Celica Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Toyota Celica Experts