While I will concede there may be conditions that I do not understand where 4:10 's will improve gas mileage and most of my driving is at 45 mph or better. I will modify my earlier post when I said there is NO WAY 4:10's will yeild better MPG, I will only say that on my IUP dash read out which has not been reset for months, it says my AVERAGE SPEED is just 37 MPH. I added my 4:10's in July. My gas mileage has dropped 2 to 3 MPG since, under my driving conditions. I believe my driving conditons are more the norm than a police car lugging around in the city. With the above said.... the 4 10's are at the top of my list for SOTP mods. I just hate to see anyone making it sound to the general public that this mod will gain you MPG. In the long run... I still say AS AN AVERAGE it will cost you MPG. BTW, if it was worth anything to the average driver... Ford would have made them standard equipment.
Scott

 

I didnt think such a big deal would be made out of my comment, but I will stand by it regardless. And for the sake of the 'general public', I will let it be known that for the most part you will lose MPG by switching to 4.10s, but it is not "impossible" to gain MPG when driving a lot in the city.

For example say you are crusing right around 40mph with stock 3.55s. You would probably be in 4th gear right around 2000 rpm, and if you shifted to 5th you would really be ******* the car, So you leave it in 4th.
Now imagine the same scenario with you driving down the road around 40mph, but this time with a set of 4.10s installed. You would be a few hundred RPMs higher then previously with the 3.55s, but now able to shift into 5th gear and now you are turning 1500rpm instead of the 2000.


BUT back on topic I found a video with a Sn197 GT with 4.10s...Its not a great video but I figured it would be better then nothing at all.
http://www.youtube.com/watch?v=ZYhQ6rlJj_Q

 

You are correct, 4:10's will USUALLY reduce mpg's. How much they reduce it depends on how and where you drive, and that will be different for everyone. I wasn't trying to start an argument, just wanted to point out that 4:10's can improve mpg's in city driving conditions. They can actually benefit you if you drive in a lot of stop and go traffic, and average speeds under 45. I think the 3:55's are a good compromise of fuel efficiency and power, hence the reason Ford decided to use them.

I drive 60 miles on the interstate each day going to and from work, and it is not worth it to me to change gears at this time to gain some acceleration, but sacrifice mpg's. Plus there is added wear on the engine from higher rpm's. If I did less highway driving, it would be worth it for me.

 

+1

I agree. Some people believe shifting at the RPM where peak torque is made will yield the best gas mileage... If that were indeed true, Ford would have written down MUCH higher recommended shifting speeds in the owner's manual and SCT wouldn't program most base tunes for 1500 RPM shift points.

In addition, 98-02 Crown Vics (4.6L 2V V8 / Ford 8.8" RWD) with stock 2.73 gears will get about 18-19 mpg city and 25-28 mpg highway. With the factory optional 3.55s, that drops to 11-13 mpg city and 18-20 mpg highway. Driving like I am driving Miss Daisy, I can maybe squeeze 14-15 mpg in the city with a tailwind coasting for several miles at a time without any stoplights.

Seeing how the S197s are gas sippers compared to my gas guzzling Crown Vic, I could live with the optional 3.55s since it will still be easier on the gas than the Vic.

 

The actual gears are cheap, but the install will put it up in the money range where you might just want to consider waiting for the tune/intake first..

 

I think it's pointless and very missleading to say that 4.10's can increase your gas mileage. CAN in theory, but usually won't. Thats probably how it should be left.

 

I think its pointless to bring this up again when we already agreed that in most scenarios the 4.10s will decrease mpg both city/hwy

 

indeed

 

I think I'm going to get the intake tune, and some UD pullies for the better fuel mileage. If I ever change my commute to where im driving 30 min or less, I will consider some cuz it sounds liek they're a blast. Thanks!

 

I did underdrives on my 4.6 2V V8 and won't ever go to underdrives in the future - not worth the hassle.

 

Sorry for the delayed response. My A/C is still ice cold.

 

Why aren't they worth the hassle?

 

I do mostly city driving and ran into some charging issues. I also experienced reduced power steering assist and reduced A/C efficiency at lower engine speeds. My batteries would not keep a charge higher than 11.7V after about 1 year of use. I have also read about oil pump gear damage from using smaller diameter dampeners at high RPMs.

I removed the Steedas and went back to stock. I did not notice any decrease in performance, but I did notice better steering assist and a fully functional charging system.