cabindoc, if you are asking me, I went with the 3.55 because at the time most of the trucks hitting dealer stock (I did not order it) had the 3.55, especially the FX4 packages. Honestly, I like it. I would want to drive a 3.31 before I would drive one. I don't tow heavy very often but the 3.55 mated to a 10K trailer is child's play. 55 to 70 mph comes on strong, getting started off the line requires a light touch unless you want to rearrange everything inside your trailer or test the strength of your hitch.

 

Well i have over 1k miles on mine now and i'm just getting around 13mpg avg for city/hwy driving. I've tried running real easy on the pedal and i don't get any better mileage. I also want to ask about another thing, as hard as it was to not "get on it" i did hold off for the first 1000 miles. but when i finally did "get on it" i notcied that the truck rpm's would only got to about 3200 rpm's. Is that normal? Also i've read about a lot of ya'll say burning rubber at will. well with the traction control of my truck will spin the tire a little but it's no drag race burn out.

 

Traction control has to be turned off, a little powerbrake to get the turbo psi up. No, it's not just plain burn out off the line but it will smoke 'em if you turn a corner or something like that.

If you are getting 13 then you should tell us what truck you have, rear end gear, and what's loaded on it. I get 13 with a light trailer, most get upper teens with a solo truck regardless of what's in the bed or what the rear end is.

Make sure you are burning ULSD and if it's winter ULSD then maybe it's just the cold weather fuel. If you have a chassis cab then it's a different animal altogether.

3200 rpm's is normal and fairly high for these light duty diesels. We get the most "seat of your pants" power between 1000 and 2000 rpms.

Second gear is where it's at in my truck. My tires break loose even with a trailer in tow, traction control or not. If I am feeling frisky I don't go 100% throttle until it shifts into second (or if I shift it in manual mode)

This is not the kind of thing I advocate unless you are a good driver and in safe conditions. We all know what we are comfortable with......

If you know what you're doing, you can go out and cut donuts with the thing. I have not pushed it to this extreme. I am pretty sure that extreme burnouts require some left foot braking.

Again, don't go out and wreck your truck 'cause some guy on FTE said to put your foot on the brake and hammer the throttle.

 

My truck is F250, 3.55 gears crew cab. It is totaly stock. Watching the fuel gage meter while driving down the interstate at 70mph it showes about 15mpg right above my avg fuel of 13.2 at this time. Last week just driving around town for 3days i avg 12.4 on the gage. Dont get me wrong i love the truck just dont know why my mpgs are so low.

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Read the sidewall of your tire. A quality tire will not go bald in the center from running it at the rated pressure (even if that's 80 psi)

Also, the weight the tire is rated to carry (again, printed on the sidewall) is only at the rated psi. Lower the pressure and you also lower the weight capacity of the tire. I wouldn't air down for towing. I'd do the opposite and get closer to max psi.

 

I'm in a similar boat. I have a 350 LWB, 3.55 gears, leveling kit and 35" Nitto Trail Grapplers (and I live at about 4500 feet elevation). I have approx 6,000 miles now and I'm still averaging 12.5 MPG. This is mostly city driving and I've only towed once (a good size boat up a big mountain). I've been told that if you tow a heavy load and break the truck in, MPG will improve significantly. I've gone through entire tanks of fuel feathering the throttle and watching the instant MPG to try to get the best possible MGP, but I still end up around 12.5 no matter what I do. I've just decided to live with it and enjoy the truck.

I am going to air my tires back up to 75 front and 80 in the rear and see how that does.