2wd 5.4L 3.55-4.10(3.9?)

bbeadel · #1 10-20-2009, 02:41 PM

I'm getting new tires on my '08 2wd SCrew. I have a 2" lift on it just because it was sitting too low for my tastes. I'm putting the 4x4 standard 275/65 R18 tires on which go from a 30.5" tire to a 32.1". Now I don't really want to sit somewhere around 3.33 and the 3.55's already aren't enough because I tow. The 4.10 gears put me by my calculations at 3.90 with the 275's. Is this too low? I'm worried about the highway mileage. If I put in 3.73's it seems i would be at 5.54 and that's lower than I am now (although not by much).
Thanks for the help!
Brandon

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06yz250f · #2 10-20-2009, 03:16 PM

a 4.10 probly would be pretty good. will give you low end back and help your city mpg's.

while towing tho, your rpm's might be hire.

but between the tire change and what not it might not be to far off from what it is now

going to 3.73's would not be worth the change IMO

glc · #3 10-20-2009, 03:41 PM

With 4.10's and the new tires, you would be turning 2100 rpm in overdrive with the TC locked up at 70 mph. Right now with the stock tires and 3.55's, you are doing 1920.

bbeadel · #4 10-20-2009, 04:05 PM

Thanks guys looks like the 4.10's will do exactly what I want them to. I can handle 2100.
I really appreciate the help!

bbeadel · #5 10-30-2009, 03:34 PM

Ok one more quick question. How do I go about getting it reflashed to match the ratio from this. The dealerships mentioned somehting about the final ration having to be one of the stock ford ones. I really don't want to buy a tuner, is there a way a service shop can reprogram my PCM for shift points/speed? What type of place should I look for?
That's my one thing I don't know anything about.
Thanks!

JeremyGSU · #6 10-30-2009, 03:48 PM

I have the oem 20's 275/55/20 and I went from 3.55's to 4.10's and my rpms at 80 is 2480ish. I have now have 285/50/20's and it's at 2505ish. However, I have had 3 sets of 4.10 gears installed at different places and all of them create drive line whine at different speeds. Just FYI. Sometimes it gets annoying.

glc · #7 10-31-2009, 01:05 PM

It's not just the ratio you need to be concerned with - it's also the tire size. You need some kind of programmer.