3.73s=increase in MPG?

40th GT:

I don't want to rain on your parade but higher numeric gears generally reduce mileage by about 1 or 2 mpg. Maybe with some tuning, mileage could be improved. With gears, the engine will operate at higher RPM's (generally speaking) so it should be more efficient, in theory. Don't take this too far, I don't mean you'll get better efficiency at 4k and should shift at that around town!

HTH,

Chris

I have 4.10's and I lost about 2-3 mpg average. About half of my driving is highway driving. I averaged about 24 mpg before and about 21 mpg now. If you don't do alot of highway driving, I would definately go with 4.10's.

I have a 116,000 mile '98 GT. It is 99% the same as it left Ford in 1998. Including plugs, wires fuel filter and even the air filter I think. The only thing not stock is the MagnaFlow cat-back and UPR shifter. About a month ago I drove it to Carlisle, PA and back. It's about 240 miles down and another 240 miles back. I gased up drove to college then home then headed out. Except for the 60 miles to school and back it was all superhighway. I got 26 mpg.

More times than I could count 5th was just too low for the roads traveled.

I will be making the switch to 3.73's this summer. With 3.27's in my normal day of driving 5th is not very useful and I have to downshift regularly. The few extra hundred rpm's the gears would give around the area and even on the highway, should equate to much less "lugging" of the engine. As you may know, lugging an engine hurts mpg. Right now I turn about 2150 rpm at 75mph. With 3.73's I would turn about 2450 rpm's. Difference is only about 300 rpm's. When I was going fast enough to turn about 2500 rpm the engine had the right ammount of power for all situations I crossed.

If I lose 1 or 2 mpg highway I don't care, but I may break even or even get 1 or 2 better around home.

40th GT said:

I was thinking that with numerically higher gears, I wouldn't have to apply as much throttle to accelerate, so I'd get better mileage. Maybe I thought wrong.

Click to expand...

No you are not wrong. It is possible to get better mileage with shorter gears. BUT it depends on how you drive. the less load on the engine for the same RPM's will show a increase in mileage, but since you are cruising at a higher RPM you will loose some of the benefit of less load so your mileage will drop.

You can see a difference with gears in the vehicle. In my 97 it came with 2.73 stock from the factory. In town I usually averaged around 17-19 depending on how i drove and even less if I romped on it enough. I took the vehicle on several road trips and only averaged around 22-23 mpg on the interstate. I thought I would of gotten better.

Then I put in 3.73's and can go through the gas fairly quick with the new found acceleration... once I got that outta the way in town I'm still about the same 17-19 and on the interstate I see closer to 24-26mpg doing 75-80 the entire trip. The car doesn't have to rev as high to go to the next gear without being too low in rpms.

I say if you drive it right you'll be just fine and should notice no difference or very little loss/gain in town.

Taller gears mean at any given point in time the engine is more likely to be revving higher.

Shorter gears mean at any given point in time the engine is more likely to be revving lower.

However, actual driving conditions vary.

But in general and on average shorter gears will yield better gas mileage.

with my 4.10's my mileage stayed almost the exact same, its all in how YOU drive the car... i short shift everywhere and shift at 2k rpm for the most part, did with the 3.27's as well.. yeah its slow but 19mpg with a v8 and the ability to blow the tires off in 1st and 2nd at will is awesome.