Hello all I have a 4.7 with factory 3.55 LSD and I used to live in southern California where my driving was 80% Highway 70 to 80 mph, and 20% city. Now I have moved to Florida where it is 80-90% city and 10 percent highway usually 55 to 65 mph. Will a lower gear ratio such as 4.11 or even 4.56's help my MPG's as long a I don't floor it from every light? It just really seems to be using a lot more fuel having to get up and moving all the time now and hitting all those city stoplight's. Thanks for any help/input.

 

Yes, re-gearing will help city mileage by 1-2 mpg, but you'll give one back on the interstate up over about 70 mph.

However, if you think you'll make back the money you spend to re-gear, you'll be disappointed. Now factor in the better performance and how it will make life easier for your transmission and it's a very worthwhile mod...

 

Well my truck never even sees 70 mph now with all the city driving. I am not worried about making my money back for the re gearing I just did not a ALL around drop in mpg's. However I know it will be hard to keep my foot out of it with the pull of new gears. I just need a good excuse to re gear.

 

i have a 4.7 too and do the same amount of city driving you do. i have 35 inch tires and was getting maybe 8-9 mpg. i put 4.56s in and gained almost 3-4 mpg in the city and 1-2 on the highway. it made one helluvah difference in drivability. if you dont have taller tires like me your mpg gained would be different though. i must say that its hard to get good gas mileage though since i love to goose it off the line and feel the kick of the new gears. I also recently did an efan mod for around 40$ and compiling the stats of that as we speak. I have a 4x4 so i had to do both diffs and it cost me right around 2100 for gears and dtts. wasnt looking to get my money back in gas saving but it was well worth it to make my truck pleasant to drive again

 

what $40 e-fan mod did you do???

 

i went to a local junk yard, pulled off a efan from a 94-95 taurus. I took one off a 3.8 v6 with around 34k on it. than i went to autozone an got a thermostatic fan controller for around 12$ and wired it through a relay so that the controller will last alot longer than wiring it straight to the power source. theres a write up around here somewhere. I roughly followed that but i riveted mine to my fan shroud instead of fabbing up some brackets to my radiator. the taurus efan fits perfectly in our fan shrouds. took some time to dial it in but so far its worked great. im currently in the process of wiring it to where it will turn on high instead of low(2speed fan) when im wheelin or towing something.

 

I would love to do that! You have any pic's?? I don't have the $$$ for a flex a lite set up but $40 is good.