I have never driven my truck with the overdrive off until yesterday and what a difference that was. I drive in fairly hilly terrain in central Missouri and usually drive around 45 to 55. I noticed that going up a hill at around 50 or 55 that I have to mash down on the throttle pretty good to keep up. With the overdrive off, I don't have to do that now. What a difference. Question: When should I drive with the overdrive on and when should I drive with it off. Is it okay to keep it off driving at around 50 to 55?

 

Yep. Just fine. Your gas mileage may or may not suffer though....

Basically, you MUST use O/D Off when heavily loaded, or towing.

Might wanna check your TV cable adjustment though......

 

I belive with O/D OFF it changes the shift pattern and goes into a better TORQUE curve for pulling things and harder acceleration to get heavy loads moving....im sure you noticed that when you turned O/D OFF the RPMs went up and the truck shifts at diffrent RPMs. But it doesent matter when you run O/D just make sure if you pull anything you turn O/D OFF. You will prabably notice a slight decrease in MPG with it off, but beings your driving hilly areas you may not even notice a change.

 

It would seem like I would get worse gas mileage overall with overdrive on, not off. The reason being because with OD on, whenever I pull a hill, it struggles. I have to mash the gas to get up, which kicks the engine in and the RPMs. In fact, the RPMs are higher when I have to do this than when I have OD off. So, it would seem like I would get better gas mileage with OD off, because I can just cruise up the hills.

 

Ive never really understood over drive. So with it off, theres more torque? On, its like "economy" mood per se?

 

Normal gears are under drive, meaning the input turns more than the output. This multiplies the torque which gives you more power to the wheels. In overdrive the input turns less than the output which reduces the torque. This lowers the motor RPMs which theoretically reduces fuel use. However under some circumstances the increase in RPMS can get the motor up into the power band which will allow less throttle and therefore fuel to be used since the motor is making more power.

 

Overdrive is pretty simple: it's 4th gear (.69:1 ratio if memory serves). With it off, your highest gear is 3rd, which has a higher gear ratio (something like 1:1, pulled a blank on that one), and thus, pulls harder.

O/D is mainly for highway driving, you get better gas milage due to turning less rpms at highway speeds, but have less power because there is less "***" turning the wheels.

Basically, it's like this: When in O/D, 5.6 power strokes in an engine revolution are linked to 1 driveshaft turn. When in third, all 8 PS's are dedicated to that same turn.

EDIT: I see someone beat me to it lol

 

I was actually expecting someone to beat me, I type slow. LOL

 

Correct now you can say you understand. On it will give you better mileage especially out on the freeways. Off is to be used when pulling heavy loads...as per others here...probably not good for the tranny to be pulling heavy loads in the overdrive on mode.

 

This is a 14 year old thread.... Please do not resurrect LONG dead threads.