2:73 Rear End Gears??????

[performancenut]

Anyone try this?

The family SUV is mainly used for trips (a Ford Expedition- not the supercharged 5.0 Explorer)

My Police Interceptor came with 2:73 rear gears and this is a 4000 pound vehicle and was originally used as an inmate transfer vehicle on flat/straight NC roads. Did OK with those gears but I still changed to 3:73 traction lock for more fun.

The main question:

If the Expedition (2003 4.6 2 WD) had the 2:73 for long distance travel, could I expect appreciable increase in fuel economy? Could I get started from a stop light in the city? No plans to tow with the vehicle; may have up to 6 passengers at times. Obviously I would reprogram for a gear change for PCM control purposes.

Any experience and opinions would be greatly appreciated.i.e. "don't do it", etc.

 

[Creager]

the 4.6 drivetrain could definatly handle the added stress. if it was a 4.0 explorer, i would definatly advise against it.

actually i would expect a decrease in mileage, unless it was a completely 100% highway vehicle.

higher gearing = engine has to struggle = high gas consumption

3.27 would suite your needs a little better

3.08 would be the highest you want.

2.73 you probably couldnt even get that motor in its useable powerband. But since it is the 4.6, it should definatly have the power to push it. It will just be slow to get going, city driving will be horrid

 

[performancenut]

agreed that city driving would be quite bad. But the manufacturer usually chooses "average" gearing that suits all-around use. So, adjusting to a primary use may actually help. The down side would be the expected difficulty in stop-and-go traffic. But, with the X-cal II, I would program/compensate for this by holding in the lower gears for a longer time during part throttle driving. Think it could work?

 

[aldive]

I would think that the gas mileage would go to hell in a handbag.

 

[performancenut]

I would think that the gas mileage would go to hell in a handbag.

OK; thanks for sharing; now why do you formulate that opinion and share the statement?

 

[aldive]

OK; thanks for sharing; now why do you formulate that opinion and share the statement?

That gearing would most probably put you out of the most efficennt rpm range for maximum or even good gas mileage.

I get my excellent mileage with 3.73 gears.

 

[performancenut]

OK; granted you are the fuel economy expert here. But, have you considered whether you could improve your situation by a 1 or 2 gear ratio change? Perhaps 3:55 could net another 1 or 2 MPG?

 

[aldive]

No; that would put me out of the most efficient power range.

 

[rookieshooter]

I just read the same general question about that size gears in an off-road mag. The head Honcho who answers those driveline questions said basicaly, hell know you would not. That if any thing it would get worse.
My own input on this is that you reach a certain point of diminishing returns on MPGs with too low a numericaly lower gear ratio in this case 2.73 Just like when I ride my bike. I'll burn more calories if I lock it in a too low a numericaly gear then I would if I move to a little higher one. Not too high not too low

 

[performancenut]

No; that would put me out of the most efficient power range.

OK. But other modifications that you have listed on your particular vehicle can adjust the "efficient power range" whether it be a subtle tire size diameter change, MAF transfer function shift, FIPK, etc. So, a gear change may actually bring the "efficient power range" closer to the level of greatest efficiency rather than depart from it. Supposedly, the PCM would compensate for small changes and bring the efficiency point back to primary use. Then, if not, additional programming would correct for that. Same differnce in programming for more HP/torque- right?

 

[spindlecone]

Great info Perf, what say you Al?

 

[performancenut]

Great info Perf, what say you Al?

al no say nuthin

 

[Creager]

Well, of course keeping the tranny in the lower gears for a longer amount of time will help the city driving... although; I would expect the city mileage to go further down the tubes at that point.

Keep in mind, with higher gears you're going to be using more power to pass on the highway. Even with your RPM being lower, your engine is going to be straining to keep up with itself. Rookieshooter got it right in his post, re-read what he has to say.

Besides, do you need to go over 80? Putting a higher gear in is going to do just that, allow you to drive at a higher speed. If you’re not going to use that higher speed, then it’s not going to do any good. It’s just going to take longer to get to the speed you do use, and make you use more gas to keep it there.

Just because the RPMs are lower, doesn’t mean your gas consumption is lower. I can see you actually saving gas by using a lower gear, which suits your target speed a little better. What is your target average speed anyway?

Wouldn’t it be easier to just put a larger tire on?

2.73 is for a 4000lb vehicle

My 2d sport is a 4500lb vehicle

That expedition has to be at least 5500

3.55 is going to be the highest you want, anything higher is going to make your engine strain, no matter little tweaks you do to it.

I've gone through this with my 4.0; I had 3.27 gearing and 32" tires… VERY HIGH, like what you want. Instead of going with a lower gearing, I put on a larger throttle body, and a better filter. I gained maybe 15 extra hp with everything I did. Sure I could burn the tires, but I was still using more gas then I was when I went with ultra low 4.56/32”.

Now the engine barely has to work, and not only do I get better mileage, I get more consistent mileage.

 

[X-North]

I own a 92 4.0 explorer with 3.73 but thuis summer i will have do lot of road trips taking 8-9 hours to do it so would it be fuel efficiency for me a 2.73 or i should stay with my 3.73 ? I have the stock tires LT235/75R15

 

[hunterdan]

Is this for an expedition or explorer? Either way I wouldn't go lower than 3.55's, only because you will be right around 2000 rpm at 65. Look at the power band for the motor, you want to be just under the torque curve when cruising at highway speeds, because when you kick it out of OD, it will be right in the power band and you will be able to pass much easier. I'm wishing I had 4.10's in my explorer, the extra gearing would be great. Around town with the 3.73s and 31's I just averaged right around 10 mpg today when I filled up. Do some research, find the power band for the motor and gear so you are just under the torque curve at highway speeds in OD. HTH

Dan

 

[X-North]

I dont think they made expedition in 1992...look at my icon...1992 Explorer I dont use my truck really in town most Higway use

 

[Drives]

You are safe putting in 3.27's, I did this in my last X. It was a 92 EB with OHV V6, I picked up over 3 mpg while driving on the highway at 70 to 75 mph.
I was thinking of doing the same thing to my current X but it's a SOHC motor and they like a little more rpm, still may try it once I get the trany fixed (It's dead). I just heard that gas will be up to $4 per gallon again this summer, and anything will help!!!

 

[Willard]

That expedition is more than 5500 lbs., I'd say closer to 6500 or 7000. That is a lot of metal to move, I would stick with the gears it has. With something as low as 2.73 I would be worried about the transmission, too.

 

[X-North]

ok i will stick with my 3.73

 

[manaen]

If you live in a flat region, and do mostly highway driving you may see a slight increase in MPG, however what nobody mentioned yet is that the cost of changing the gears would take years to recoup, so in the long run I would stick with the gears you have. If you want better gas mileage get a shoebox

And as everyone alread said your city mileage will suffer.