What does turning overdrive off do? I hear people saying turn it off. why?

 

It gets you better gas mileage on the hwy. Turn it off when towing.

 

if not towing should I turn off on hwy?

 

Only in hilly areas

 

ok thanks!

 

When you feel that the engine is lugging, running right at that shift point (2000 rpm's) and on long grades, it is a good idea to turn it off. I run on Interstate 8 from El Centro, CA 100 miles into San Diego. The drive starts below sea level and temperature above 110. The road climbs to 4000 ft above sea level and the grades are pretty long and always windy. I have the overdrive shut off going up and turn it back on at the top. My mileage is usually around 17 - 18 for the total trip.

Utah has a lot of long grade hills. The members that are here that are from the east coast do not have the same kinds of grades or wind issues that we do here in the west. Again, turn it off if you feel like you are lugging or right at that point where the transmission will be constantly shifting down and up.

 

ok thanks really helpful!

 

Turning OD Off forces the transmission to NOT use 4th gear. Simple as that.

If you find that you are constantly dropping in and out of OD, reach down and turn it off to prevent extra wear and tear, and to keep the tranny from overheating.

If you swap to taller tires and do not re-gear, you can turn OD Off as a means of getting better freeway rpm's.


In the Drivetrain section of the Modified FAQ's, you will find a great rpm chart. Measure your tires to get the 'actual' height, then plug it into the chart to get your OD ON rpm. Divide that number by .69 to find what your OD OFF rpm's will be.

 

Exactly; just like cruising in 5th on the highway when the terrain is hilly and not using 6th gear in the manual trans JKs. Keeps your RPMs higher and thus the motor spinning in the powerband. The old 4-speed auto often takes it's time to kick down to 3rd on the highway when encountering a hill or overtaking/passing, which gives the autos such a sluggish feeling onroad. It will also often change back up to 4th earlier than it should, causing a loss in momentum and power and result in the gearbox hunting up and down between 3rd & 4th trying to find the correct ratio.

They say the new 5-speed fitted to the 2012's is a huge improvement over the old box , as it has that extra ratio to play with. It's the reason why most of the complaints about the 3.8L being "underpowered" usually come from the auto drivers & not those with the 6-speed. The 4-speed auto's tall overdrive ratio coupled with the tall factory diff gearing is not an ideal setup for something with the aerodynamics of a barn door and the power to weight ratio of the JKU.

 

Is there a way to default the OD button to off?