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  #1  
Old 10-18-2010, 09:34 PM
trucksrford trucksrford is offline
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Default Is it possible to change the axle ratio without screwing up the emissions?

Looking at purchasing a 2008 Ranger which has a 4.1 gear ratio. However, I would like to put the 3.73 in for better mileage.
The speed censor on the axle, would be changed too, but that would be all.

How much would this mess up the emissions and make the truck run poorly?

If it would run poorly what would have to be done to correct it?

Has anyone done this?

Thanks.

Darrel
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  #2  
Old 10-18-2010, 09:40 PM
Fx4wannabe01 Fx4wannabe01 is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

How would gear ratio change how the engine runs emission wise??





You'd probably want to either bump the tire size up or have your computer flashed to reflect the axle ratio change to keep a correct speedo and trip meter. Has nothing to do with emissions. The rear ABS speed sensor are all the same 98+.....that's not where your speed signal is taken from though. Your trans output shaft tells the PCM the speed and then it sends it to the gauge cluster. I believe the ABS module is also sent this information to compute what it has to do with it and what it's getting from the rear axle. But don't quote me on that.

BTW......What engine and trans?? If 2.3L Auto, you're gonna want to keep that 4.10 ratio back there for both driveability and economy.
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Old 10-18-2010, 09:42 PM
trucksrford trucksrford is offline
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Default

3.0 Liter with 5 speed Manual.

That was sort of my feelings, however, I ask a mechanic and they felt with all the electronics and feel back circuits the truck wouldn't run well.
I don't know if they didn't want to have to fix something I broke, or they were really serious that things would get messed up. We only had a couple of minutes to talk.

I have changed the axles out before but that was before they had computers.

PS. Thanks for the reply.
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Old 10-18-2010, 10:05 PM
Fx4wannabe01 Fx4wannabe01 is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

Tossing on a higher(numerically lower) gear ratio is alot like tossing on smaller tires....aka doesn't do anything bad but throw off the speedo by whatever the difference in the original tires and the new ones. Gear ratio changing....same difference.
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Old 10-18-2010, 11:22 PM
TheStig TheStig is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

if your mechanic is saying a simple axle /gear swap would change emissions and mess up your electronics....i would HIGHLY advise you to get another mechanic, cause that one is retarded
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Old 10-19-2010, 04:43 AM
ranger024x4 ranger024x4 is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

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Originally Posted by TheStig View Post
if your mechanic is saying a simple axle /gear swap would change emissions and mess up your electronics....i would HIGHLY advise you to get another mechanic, cause that one is retarded
this.
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Old 10-19-2010, 04:47 AM
FireRanger FireRanger is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

Quote:
Originally Posted by TheStig View Post
if your mechanic is saying a simple axle /gear swap would change emissions and mess up your electronics....i would HIGHLY advise you to get another mechanic, cause that one is retarded
x3.
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Old 10-21-2010, 04:03 PM
trucksrford trucksrford is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

I am waiting on a request to a Ford dealer is they would have to change the information in the computer to keep the Speedometer and Odometer accurate or it the sensor in the rear axle would take care of that.

Thanks for the replies.
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Old 10-21-2010, 05:15 PM
FireRanger FireRanger is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

It's a computer setting. You can also buy a programmer (like an xCal or similar) and change it yourself along with many other performance related changes. I'm curious how much the dealer will charge for that. The programmers are in the $300 range.
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  #10  
Old 10-21-2010, 05:49 PM
mickblock mickblock is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

Don't waste time and money swapping to a 3.73 for the sake of MPG. The small difference won't be worth it for that reason. Your over drive transmission more than makes up for it. Do a web search for "final drive ratio Vs. MPG."
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Old 10-21-2010, 06:04 PM
bilko1 bilko1 is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

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Originally Posted by mickblock View Post
Don't waste time and money swapping to a 3.73 for the sake of MPG. The small difference won't be worth it for that reason. Your over drive transmission more than makes up for it. Do a web search for "final drive ratio Vs. MPG."
I have been reading this with some intrest, If changing the gears wont help with MPG, what mods, without spending a ton of $$$ will help out?
I get 16 to 17 MPG no matter how I drive or what fuel and or addatives I put in. 2wheel drive or 4wheel drive it never changes.
I have 2001 XLT 4x4 with 4.0,
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Old 10-21-2010, 06:16 PM
mickblock mickblock is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

I'm not the guy to ask that question. Since I'm not an aftermarket engineer, I'm resolved to assume that the best place to put your time and money to achieve better gas mileage is in maintaining your truck.
If your mileage doesn't decrease due to lack of maintenance, then over time, you've made an improvement.
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  #13  
Old 10-27-2010, 08:16 PM
trucksrford trucksrford is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

Hi,
Sorry no response from the Ford dealer yet.

However, I know in the old days, without making any changes other than the rear axle ratio, ie 3.73 to a 4.10 the gas mileage always went down. However, you got off the line faster with the additional torque. And I notice with Ford when you change from a 2wd 2dr to a 2wd 4d, it seems they move you to a 4.10 with an auto with OD and the best MPG you can get drops to 19. Yet with the 2dr (and a 1.43 HP or 148 HP) you can get 27 or 24 MPG based on some claims. Seems to be a really big drop in MPG if you compare the 3.0 with the overdrive, a 4.10 axle and the weight of 2 extra doors, that's 5 MPG and it just doesn't seem right. I would like to know what I could get with the 3.0, 5 speed manual, 2wd 4dr and the 3.73 axle. If I don't have the computer flashed, it seems it would just be the speedometer and odometer that would be off. If that's the case, my GPS could replace those two instruments! It's seems to be right on most of the time!
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Old 12-28-2010, 04:56 AM
trucksrford trucksrford is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

Ford Dealers cost to reprogram the computer is $130.
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  #15  
Old 04-25-2011, 05:45 AM
wilsonbh wilsonbh is offline
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Default Re: Is it possible to change the axle ratio without screwing up the emissions?

I have a 2000 Ranger (v6) and I am very unhappy with the gas mileage. Seems to always get about 21mpg, or less. I have the extended cab with automatic transmission with Overdrive. However, when starting off, it sounds like the engine is racing (high RPM) and I'm barely moving. Am wondering if the rear end might be a 4.10? It is a 2wd vehicle. I know someone that changed out their rear gear and their gas mileage jumped up by 10mpg. So I'm researching if this might work for me. Any advice would be appreicated.
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