LaxAHolic

im really having a hard time with this o/d stuff. when do i turn it off? what does it do? please be gentle, never owned this kinda of vehicle before..

ronjenx

Overdrive allows the engine to turn slower for a given road speed. In the automatic, 3rd gear is 1:1 ratio, engine and drive shaft turn the same speed.
When in overdrive, the engine turns 0.69 to one turn of the drive shaft.

It is there to save a little fuel, as the engine turns slower. (Mostly for highway speeds.)

I turn mine off around town to keep the transmission from constantly shifting into and out of O/D.

You would turn it off if towing a heavy trailer, even on the highway.

racer83l

mine is off every time I hit the highway... with 35's and 3.73 gearing, the engine cannot keep the JK at speed.

I like it off and am debating having the local dealer shut it off permanently.

NorthRiver

I turn the O/D off every time I drive my jeep,and I'm only running 32s.

I've actually picked up 2+ mpg since I started running with the O/D off.

The engine is closer to the powerband and its not constantly shifting in/out of O/D.

ronjenx

Didn't know they could do that.

I would prefer to have it default off, so I could turn it on when needed.

Someone installed a delay momentary relay that would shut off the o/d about 3 seconds after startup. Then he could just hit the button to turn it on when needed.

BBirish

I also turn it off every time i get in the jeep. 35s and 3.73 gears, definitely keeps the rpms where they should be for this set up

Vaughtra

great post and great advice---so driving on a long trip on the highway, definately turn it off??

ronjenx

Where did that come from?

What I read in all this is:

If you are stock, have it off around town. Have it on for the highway.

If you have bigger tires and not the gears to compensate, turn it off all the time.

Vaughtra

I guess I pulled it from this. I have 32's. I don't know anything about this so my previous comment was more of a question

PG-JKU

You cannot take another person's experience with running without overdrive and apply it to you without considering the type of terrain, traffic (stop and go) average speed, set up of jeep etc etc. You're going to need to sort out things on your own.

I have a 6 speed and find that the jeep runs best between 2500 and 3500 for instant power, but for long highway stretches there's nothing wrong with using your gears to putz along at 1800 rpm (6th gear for me). That should get you the best mileage if that's what you are after.

Mileage and power are usually mutually exclusive. Pick one.