Sport Trac Rear Ratio - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

braunstein82 · 02-05-2009, 09:27

i GET CRAPPY MILAGE ON MY 05 SPROT TRAC 2WD. Wanted to know if i lowered my rear gear ratio would i save gas or do worse, has anyone done this? And what is the stock ratio?

braunstein82 · 02-07-2009, 04:41

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**360ci** · 02-07-2009, 19:07

In '02, Motor Trend rated a combined mileage test with a similar vehicle (2wd 4.0L V6) at a mere 16mpg. That was the city rating, so is considered to be average. Curious to know what mileage you net with your ST?

Back to gears: If you drive mostly city mileage, upgrading to a 4.10 or 4.56 (if you run over sized tires) will net better economy as you'll get the vehicle up to speed faster than if you stayed with the stock 3.73/3.55 gears. If you drive a lot of highway and don't have problems now with gear hunting, you could also get a taller gearset. However, that will lower your city mileage and the engine will work harder to get the vehicle up to speed. A good site is Yukon Gear & Axle to find available ratios and other related parts.

To find the stock ratio, you can do three things:
1. Email Ford and request a factory build sheet, they'll take their sweet time getting it to you (about a month)
2. Take the differential apart and calculate the rotations relative to the driveshaft (can be hard without the proper tools/math skills)
3. (easiest) Look in the glovebox for a sticker that should have the ratio listed on there.

braunstein82 · 02-10-2009, 04:59

i get about 15 city and 17 hwy on a good day. If i put the bike in back it goes about 12 city and 15 hwy.

i thought a bigger gear ratio would cause worse gas because the engine is at a higher rpm just to go the same speed

**jwko** · 02-11-2009, 22:51

Count the teeth on the ring & pinion and divide to get the gear ratio.

braunstein82 · 02-12-2009, 05:00

bump

**360ci** · 02-19-2009, 11:26

Quote:

Originally Posted by braunstein82

i get about 15 city and 17 hwy on a good day. If i put the bike in back it goes about 12 city and 15 hwy.

i thought a bigger gear ratio would cause worse gas because the engine is at a higher rpm just to go the same speed

Higher RPM's at a given speed don't factor into burning more fuel, throttle position does. The more you put your foot into it the more fuel you'll consume. If you drive in 3rd gear instead of over drive for a few days I'm sure you'll get similar mileage unless your commute is strictly all highway. There are a lot of variables involved when it comes to fuel economy. Again, the SportTrac isn't rated much above 18mpg in 2wd 4.0L V6 form as it's based on a truck platform. I don't mean to sound crude here, but one doesn't buy a truck for fuel economy, you buy it for purpose.

When was the last tune up done - ie. new plugs, air filter fuel pressure check etc? Routine maintenance can sometimes boost mileage. Depending on the weight of your bike, mileage will drop accordingly. If it weighs 400lbs, that'd be like adding a few passengers inside the vehicle. Depending what highway speed you drive at (below 65mph with any load will greatly increase mileage)