gas mileage and differentials

[Kaka-x]

I was driving and saw a tranny shop billboard flashing messages about changing your differential gears/ ratios and improving your gas mileage.
Does anyone know about this and has anyone done this to their explorer and if so could you share this info as it will be a big help to all.
i like my explorer she is in very good shape but i want better gas miliage than what i get so far and dont want to sell her and get a tin bucket.
98 x 2wd ohv

 

[unclemeat]

Changing gear ratios may help improve your fuel econemy. It depends on tire size, axle gear ration, and driveing habits. It is unlikely that a stock explorer would improve fuel mileage. I saw a substantial increase in gas milage when I regeared my X, but I am running a 33-inch tire (not stock).

A better solution to improve gas mileage would be synthetic fluids, high permance intake and exhaust, increasing tire pressure, ect. This issue has been discussed on this site.

 

[kfkodiak]

Regearing can be $$ if you have a shop do it, so even if you see an increase in fuel economy it will take some time to recover the cost. Here's a basic rundown on common gear ratios for Explorer axles:

3.08 | Low Highway RPM / Better Fuel Economy
3.27 | \/
3.55 | \/
3.73 | \/
4.10 | \/
4.56 | Greater Towing Power / Acceleration

 

[Ray Lobato]

My truck came stock with 3.55 gears and with stock tires, it would get around 23 to 23 MPG at 70MPH.
After I modified it for offroading, it now gets 15MPG. That's with 4:10's 33x12.5 15's and about 600 pounds of winch, armor, and Atlas II transfercase.
There are better ways to increase gas mileage than messing with gear ratios.
UncleMeat gave you a good start.

 

[MuNkY6913]

yeah i know its a really old thread. I bought this truck a couple months ago. it already had 33x12.5 tires on it. It just feels so sluggish. the guy before me just lifted the body 5 inch and slapped on the tires. pretty sure nothing was done to it suspension or drive train wise. it also has trouble deciding what gear to change into. it wants to up shift but as soon as i'm on an incline it shifts high then low then high and does that a few times and the od light starts flashing. the abs light has been on since i bought it too. seems to accelerate ok when on a flat but as soon as i start an incline it starts to slow down. i'm guessing i maybe get 100 miles to a tank. i'm also running around at 3k rpm all the time cause of the mountains around here and it not being able up shift. the guy said he checked and replaced a few of the abs sensors and they're working so hes not sure whats wrong. any other threads with this would help. i searched but this was the only one that came back in the results.

 

[koda2000]

the large diameter tires effectively lower your gear ratio. this will make the truck feel sluggish and make it downshift out of high gear (forth or fifth depending on which your trans you have). not running in high gear will raise the engine RPM and adversely effect fuel mileage. if your truck has 3:73 differential gears, you may need to go to 4:10's with the larger tires, or go down to a smaller tire (31's or 30's for example).

the larger tires shouldn't be turning on the ABS light though, unless they're not all the same diameter. they will mess up your speedometer though (unless you tune your PCM parameter for the larger tires).

 

[drdoom]

Yes as koda said, unless modifications were done to account for the larger tires, all sorts of trouble with shifting and such. Using the lowest gears posted above, and corrections to the speedometer and or PCM is the right way to do it. There is tons of info here about this, do a bit of searching in the 2G modified forum.

 

[MuNkY6913]

[MENTION=29519]kod[/MENTION]a2000 and [MENTION=75839]drdoom[/MENTION]. thanks for the help. i saw somewhere, i think a thread about the tranny shifting problems, that the abs and speed sensor are one and when something isn't spinning as fast as it should that will keep the abs light on or something. cant find where i saw it. i'll check out the 2g modified section and see what i can find. just want this thing to run right. it only sees about 3 miles a day as it is my winter beater but i still want it to run right. thanks again guys!

 

[SoNic67]

Is not that simple.
What you gain on highway, you will lose in city driving... all those 40mph roads might be driven on third gear. Also acceleration from dead stop (stop lights or 4-way stops) will take longer, spending more time in lower gears and higher rpm's.

 

[MuNkY6913]

Is not that simple.
What you gain on highway, you will lose in city driving... all those 40mph roads might be driven on third gear. Also acceleration from dead stop (stop lights or 4-way stops) will take longer, spending more time in lower gears and higher rpm's.

what do you mean? city driving isn't a problem. no problem taking off slow from a stop light. the problem lies in going up any incline at speed higher than 30 or even maintaining 30. just has no gumption on an incline

 

[SoNic67]

Yes, you are taking up slow. Takes a long time. In 1st and 2nd gear. And your mileage will be low because of that.