Explain how my Overdrive works!

[OilPatch197]

What OD is to do is run the engine at a slower rpm and save fuel.

...ok but let me describe what happens in MY truck, a '87 with a 2.0L and 5 speed.

I am at 55mph, when I shift into OD, I have to PRESS DOWN FURTHER on the GAS to maintain the 55mph(this is on flat road)

So is it better to run at 55mph at high rpm or to run 55mph in OD and seeminly using more gas.

How does this work, that the higher rpm 4th gear requires less throttle than OD.

 

[scotts90ranger]

yes, run in 4th, the 2.0/2.3 won't care, it'll live forever...

back in the day when I actually got decent mileage I got better mileage in 4th than 5th, and even now with my current combination it takes less power to run in 4th than in 5th.

if you went down in tire size a size or two it would probably run fine in 5th.

 

[2manyfords]

I'm some cases the engine is not powerful enough to use OD such as a 2.0L ( I had one a few years back) therefore you have to put more throttle to it to maintain speed.

In those years of trucks Ford didn't always use correct gearing for the best fuel economy.
Why did they do that? Who knows, testing in a lab is different than real world situations.

I also owned an "86 Chev full size truck with a 305 with a 700R Automatic and I couldn't use OD because the fuel economy was terrible. It got 11mpg in OD and around 18 to 20 MPG without OD. These are Canadian gallons.

 

[feellnfroggy]

Your best fuel economy in a small motor like that will come from around 2500-3000 rpms. When your doing 65-70 and its in OD thats about where your rpms are, any lower than that you wanna run 4th.

 

[Jay FX4]

This isn't a direct comparison, and we're dealing with different engines, but I had a similar thread a while back that might be worth reading:
http://therangerstation.com/forums/showthread.php?t=55545

 

[OilPatch197]

Your best fuel economy in a small motor like that will come from around 2500-3000 rpms. When your doing 65-70 and its in OD thats about where your rpms are, any lower than that you wanna run 4th.

Well I can't drive that fast due to all the flat spots on my tires! I usually start the truck with the clutch, and sometimes my tires bark.

 

[Louisville86]

I used to own an '85 GMC S-15 Jimmy (think S-10 Blazer) with the 2.8 carburetor, 4WD and the 4-speed automatic. I think it was 120 horsepower in a fairly heavy little truck, that that thing was unbearable on the highway. Maintaining 60 or 65 was constant "hunting" back and forth between third and fourth (overdrive) gears. What a dog that thing was. No power and the mileage sucked (12 or 13 in mixed driving). Good riddance!

 

[bbbb51]

I had the same problem with a 89 blaser 4x4 5 speed. It would not even be able to hold the speed if u shifted to fifth unless u were going downhill. WHAT A POS IT WAS.

 

[exbass94]

I used to own an '85 GMC S-15 Jimmy (think S-10 Blazer) with the 2.8 carburetor, 4WD and the 4-speed automatic. I think it was 120 horsepower in a fairly heavy little truck, that that thing was unbearable on the highway. Maintaining 60 or 65 was constant "hunting" back and forth between third and fourth (overdrive) gears. What a dog that thing was. No power and the mileage sucked (12 or 13 in mixed driving). Good riddance!

My father used to have an 85 S10 Blazer. I was way too young to drive it, but I remember my mom always complaining about how slow it was.

 

[LearjetMinako]

The 2.0 has barely any power to use the OD. Even with my 2.3L, I know what you mean by you have to push the pedal in a little further. I guess the theroy is that the less rpm's have less pulses of fuel. So that would be less fuel overall.

Just remembered something. That 2.0L is a carb-ed engine right?

 

[BRUTUS_T_HOG]

well lower rpms means less engine wear, in a higher powered engine OD does save fuel but not in an under powered engine.

i think ranger OD is about .70:1, my 2.3 with 3.45 gears pulls 5th just fine but i've had a vacuum gauge hooked up at 55mph on flat ground and i get about 15" Hg. in 5th and over 20" Hg. in 4th so that is proof that 4th is more efficient