Hey guys, I've been 'hiding' on here for a while now, just decided to finally get some things done to my truck that I've been putting off.
I have an 04 Scab Fx4, (3.55 gears) and by the end of the week I will hit 100,000 TROUBLE FREE miles. I pull a 2000lb cargo trailer daily on a 150+ mile round trip. On weekends I pull a similiar trailer with my dirt bike racing gear, (bikes, water barrel, pressure washer etc). As of right now, I'm buying a tank of gas about every 2 days. I'd like to save some money on gas, but I'm a firm believer that throwing 'mods/$$$' at a truck to get better gas mileage isn't exactly the smartest decision by the numbers. I have a 26 gallon tank, on average i get about 300 mpT. Thats working out to about 13mpg (23gallon fill up) average while pulling trailers. My truck is RARELY if ever driven without a trailer. Maybe 30 miles a week is trailer-less. (but on my long trips trailerless I get about 17.5 - 18 mpg, really good mpg as far as I'm concerned)

OK now the questions. I have BFG At/Ko tires on the truck (285/75R17 = 33x11.5). I'd like to lift my truck, (not a leveling kit) and put 35's on 18's on it. What kind of decrease in mpg am I going to see with this? The truck will be higher, and have larger tires, requiring more shifting and more time in lower gears, so i know it's going to negatively effect mpg. Would installing 3.73 or 3.92 gears help me neutralize that? As much time as i spend hauling, 3.92 gears might give me a small increase in mpg. I dont have time to run the ratio's right now, but off the top of my head, 3.92's with 35's should be close to the stock final drive ratio, correct?

Also, a front end guard/ grille guard/ brush guard. I've been considering this a while, I like the Warn model, but do I need a winch... maybe.. especially if I keep this truck as long as I'm intending to. Because at 250,000miles, I'm treating myself to a new f350 and retireing this one to the 'hunting truck' position. How much weight and drag would a brush guard and winch add? Every 400lbs steals 1 mpg... so probably about 1 mpg decrease.. hmm.... any thoughts?

help me figure this all out guys! thanks

 

I have an 04 fx4 fabtech 6 in and a lot of mods. If you want 35 in tires to get you back to stock you would be looking at 4.10s. I have 4.56 gears, they will hurt you on the freeway, the power is geat. If they are made, I couldnt find them when I lifted my truck, try to get 4.30 gears, that would be the best match for what you are looking for. That is just a little over stock. My MPG's went from 17 to 12. The weight of the tires and the extra weight from the added lift is around 500 lbs, give or take. The truck, if you go with a lower gears or change tire size, will need to be reprogramed, which you can do with almost any reprogramer out now. This process is not cheep so be ready to spend some $$$. You will need to change out the 3.55 gears, figure at a shop it is close to 1,400 to 1,500 for parts and the work. figure the reporgramer will be around 350 or close. The lift and tires there is a huge difference between all places but look around I got some great deals. Do not expect to add any MPG increase by lifting and changing gears from what you have if you are lucky you will be close to what you have now. check out my gallery.

 

I put a 6" lift in my truck and i lost about 1 mpg after i lifted it. Two weeks after i lifted it i installed the edge programmer and since i did that i gained about 2 mpg. I don't know if it's because i changed my driving style but with the Edge and the lift I am 1 mpg better than when i was stock.

 

I just realized something. My MPG numbers are being based on stock computer settings. hmm.. To have 33's, I'm really not doing bad on gas mileage at all.

According to the calculators, my effective ratio as we speak with 32.9inch diameter tires is 3.24.... GRRRR now i KNOW i need to regear! Im kinda surprised i've had no trans problems with that low of a ratio!

So if I go with 35's, I'll need 4.10 gears to get me back to about a 3.5(5) ratio, and a 4.30 to get me just a tad shorter than stock for my truck. hmm.. looks like 4.30 is the way I'd like to go. Thanks for the input on that question! Any one have a good source for gears for front and rear? btw- what front end is in this truck???