Is it important to do that?

With the overdrive mode OFF, you wo not get as good gas mileage as if it were on. The times when you might need to use it is when you need a little bit more power from your engine at low speed or when you need a little ''engine-braking'' to slow or stop your car.

Turn the overdrive off when the transmission is constantly changing gears. You can hear the sound pitch of the engine change when the transmission has changed gears. This commonly happens when u r driving in heavy traffic & making many stops. l turn mine off when l am in a traffic jam, on a busy street with a lot of red lights, & when l am coasting downhill on a winding mountain road. Turning off the overdrive in these situations will save wear & tear on ur transmission. This applys to all vehicles with automatic transmission with an O/D OFF button. The feature is integrated in the onboard computer. Just do not forget to turn it back on when traffic is smooth again. You will get poor gas milage if u don't. (Milage is not affected in heavy traffic because heavy traffic already gives u poor milage)

Unless you're towing a trailer or driving in the mountains, leave the OD on.

M

Basically in low load driving situations, this means, in effect, on freeway driving. O/D should not be used in traffic, hilly or mountainous terrain, towing, ect. these conditions are somewhat hard on transmissions (and engines) when in O/D mode.

According to my 1994 Town Car owners manual you should turn off the over-drive when you are basically in town (driving under 40 mph) it keeps the trans from shifting back and forth between 3rd and 4th (OD) gears. My city speed limit does not go above 35 mph. If you do not have the owner is manual most junk yards will sell you an owner is manual for $5. It is well worth it to know what is best for your car.

simple... overdrive off in town(stop and go traffic), and overdrive on when cruising at highway speeds.

l would not even touch it unless u r towing a heavy trailer that causes ur tranny to shift excessively or if u r going up hills that cause excessive shifting. If u r in city driving overdrive is the final gear & when driving slowly in traffic, ur car should not be shifted into overdrive anyways even if u have the overdrive mode on. l am also pretty sure that the tranny is a 4 speed with overdrive. l would not bother turning overdrive off while going down hills, it is cheaper to replace brakes & rotors than it is engines & transmissions. Turning overdrive off going downhill will only rev up ur engine more causing more wear on it as it will be working harder. If u r going downhill with a heavy trailer than that is different, but than again with a car u r not going to be towing a heavy trailer. With cars though, a light trailer will be noticed while towing so what l am implying is a heavy trailer for ur vehicle when comparing it to ur towing capacity. LOL. Really though, just turn overdrive off if u r in hilly areas where ur tranny shifts out of overdrive & back into overdrive a lot. Other than that, do not mess with it.