Originally Posted by ronspradley
What kind of transmission are we talking about here? Do you have the over/under drive that is mounted at the rear of the transmission? Or are you saying the Ford transmission that you have has this in or out switch on the dash?
I am confused.
I believe what ronspradley is getting at is if it is an overdrive in the transmission, then the overdrive is simply a fourth gear which allows the output shaft of the transmission to rotate faster the the rpm of the engine.
If it is an add on unit behind the transmission then it is what is considered an under/over drive which is manipulating the output of the transmission.
The overdrive in the transmission will not even affect drivability in most city driving situations as the transmission will not switch to the overdrive until the vehicles speed is high enough to do so.
An under/ over drive unit will affect your final drive ratio in all situations and would be better left in the off position in town, on steep grades or while towing. In flat highway scenarios you would be better off having the overdrive engaged.