Ok, I must admit that I don't know much about this. Can someone give me a clue as to the difference between the 3.55 and 3.73 ratios? What are the advantages/disadvantages with either? Thanks.

 

It affects how fast the engine spins compared to the wheels. The higher the number (3.73 in your comparison), the higher the engine speed at any given vehicle speed. This would yield better acceleration, but potentially lower fuel mileage. There are many exceptions so the key is to match up a good combination of gear to engine. The 5.4L requires at least 3:73 IMHO and the 4.6L seems to work better with 3.55. The acceleration from a stoplight is much less, but once moving, the 3.55 geared truck can be taken out of overdrive. This will make the engine speed run higher with good power, but not as high as 3.73 out of overdrive.

 

APT, could you explain a little mre why you think the 5.4L should be paired with the 3.73? I am a noob to truck buying, but I am set on an '04 F-150, so this is me doing research. thanks.

 

It really depends on what you'll be using the vehicle for. If you want to tow or haul heavy loads, get a higher gear ratio. If you want better fuel economy on the highway under light loads, get the lower gear ratio.

 

The 5.4L likes to cruise in the 1800-2300 range. If you have to drop it out of overdrive on the highway in order to keep a decent speed, you'll be 1000rpm higher which the 5.4L doesn't like to much. It'll do it all day long, but you can watch your gas gauge drop by the mile. Also, under normal times when not towing in town, the gearing and torque will allow the tranny to shift rather low and yet have decent acceleration. If you don't have to push on the gas as hard, you can actually get better fuel mileage than an underpowered vehicle because the driver is compensating by revving too much. This is highly dependant upon driving style, though. Whatever yor choice, make sure it has limited slip.

 

Just so there is no confusion, lower gears are numerically higher (ie, 4.10 gears are lower than 3.55 gears). For towing and acceleration, lower gears are more effective. For fuel economy and frequent freeway driving, higher gears are more effective. But, it all depends on the transmission and engine, too as someone else was saying. For most V8 engines, 2000 rpm is a great cruising rpm on the freeway. It just depends on what your uses are and what your priorities are. I have 4.10's stock but after I get my 36's (in a few years), I'll be swapping in some 4.88 gears. My priorities are NOT fuel mileage, but rather acceleration and low speed power!

 

for me i would be hauling stuff in the bed a couple of times a month. 500lbs at most, so nowhere near the limit. i won't ever tow anything. and definately some freeway driving since i am in LA. gas mileage is important. so by this description, would you all recommend the 5.4L with the 3.55? and since I am not going to tow, is the limited slip worth it? feel free to weigh in, all input is appreciated.

 

I would say that the 3.55's should suit your needs. The LS is for traction. The people that value this the most are the ones who like to go off road or street race, but it can come in hand during adverse weather. Although you probably don't see too much of that in LA.

 

P.S. Are you planning on getting a 4x4 and lifting it? If so, lower gears are crucial for mounting large diameter tires. Just thought I'd ask.

 

good thing you asked because that is exactly what i would want to do. i think an occasional (like once every year) 4x4 outing will happen, but that will not be the primary use. i will never take it in mud and water becasue i am not a swamper. i want to lift it a few inches and put some bigger tires and better rims. that way when i go offroad in the dirt and sand i can have a good time. so, this being the case, your recommendations are...?

btw, thanks for all the help guys. i really appreciate the education. i am also doing a lot of reading on www.howstuffworks.com. it is such a great site, to learn from. they have a great section explaining open differentials and LSD. i highly recommend it if anyone is clueless like me.

 

I would say I am sold on the 3.73 gears as that is what will be in my truck that is on order. The reason im so sold on them is that I have had a 97,99, and a 01. The 97 had 3.55s and the 4.6 and was neither powerful or good fuel wise. The 99 was the best and it had 5.4 with 3.73s and it got around 17 to 20 mpg no matter how I drove it. The 01 is the same exact truck as the 99 but that year they didn't offer the 3.73 (has the 3.55) and I can tell a big difference in the mpg and the power. This truck (01) is lucky to get 15 mpg and is way less powerful in accel and seat of pants feel. Like mentioned before the 99 you didn't have to give it much pedal to take off and it shifted faster, I would guess using less fuel. On the highway it felt like it was always in the sweet spot and never would kick down like the other two seemed to way to often. I know that the new truck has packed on a few pounds and probably wont have the seat of pant feel that the 99 had but with the three f-150s that I have had there is no way I would go with anything but the 3.73ls that is offered. Hope this helps but after all, all trucks are not exactly the same even if they are the same year and model and this is just my experience with the three previous trucks that I have had.

 

Well, I guess it depends on how big of tires you want to put on there. I would say 3.73's are fine up to 32" tall tires. For 33's, I would go with 4.10's and for 35's I would go with either 4.30's or 4.56's depending upon how serious you are about performance. You can get away with 4.10's and 35's (that's what I'm running right now) but just keep in mind that my truck came stock with 4.10 gears and 29" tall tires, so 35's are a significant blow to my performance. Now I know that you won't be able to get 4.30's or 4.56's stock, so if you really want to go big you have to pay the price. My recommendation is to get as low as you can from the factory (3.73 or 4.10) and with that new 300 hp 5.4L engine, you should be able to turn 33's with no problems. Hope this helps.

 

Brewmaster, if you plan to buy a little larger larger tires than stock, get the lower (higher number) gear. If you plan to go with a lot larger tires, then you may be replacing the gear aftermarket anyway. I have an 03 Supercrew 4x4 with 3.73 gears and 285/75R17. It seems very much down on power and fuel mileage compared to my 99 Supecab with 1" smaller tires and 3.73 gears.

 

thanks fellas. this is why i come here to ask my questions. i don't think i'll go up beyond 33's. in fact, i highly doubt it. when purchasing does come around, i'll definately go with the 3.73. but that won't be for several months. thanks again for all the input.

 

What would you recommend for the following usage for a FX4 4x4 in my situation described below:

I own a horse so you know that I will be towing "almost" on a pretty regular basis. Seeing as how most of the time I buy in bulk my feed (one bed of feed can last a few months) I don't really expect to have to carry much "all" the time, but when I do it'll be a lot and I intend to trailer my horse to shows which happen a few times a year. Fuel mileage also isn't exactly my biggest concern and I'll be getting the 35.7 gallon tank upgrade. I'd sacrifice gas for power and acceleration

I also intend to lift the truck a few inches and put tires on them just a little bigger. I also intend to boost the horsepower from 300 to 350-400.

So, I don't really want to substitute acceleration, but will my needs require that I do? And, since I'll be boosting the horsepower will that make any difference?