Guys, haven't posted in a while, still looking for an '03 SCrew with 5.4/3.55's, sliding rear and 6 pass seating between 25K and 35K miles.
I have found several trucks that fit all that except they have the 3.73 so, I've passed on them. Now, I'm really starting to get frustrated, just passed on another. I'm not that concerned about fuel economy, if I was, I'd be looking at a Focus or something. I just want to do the best I can in terms of gas mileage, with the truck I buy. My daily commute is 33% city, 66% hwy 5 days a week. Other commutes usually entail mostly hwy driving so I believe the 3.55 is the way to go. plus, I rarely if ever tow, just occasional mulch, lawn equip to the shop or appliances. Should I be so hung up on the 3.55? I'd like to put bigger tires on the truck when I get it. I understand bigger diameter tires put the load back on the engine and usually kills city mpg's, makes performance a little sluggish (off the line), but sends hwy mpg's up pretty high...again, for a truck. Does anyone have any experience with bigger tires on the 3.73? What does that do to fuel economy? Do you lose performance? Maintain performance? I want to make sure I'm not insisting on the 3.55 only to find out after the fact that the 3.73 provides the most flexibility. Your experiences would be greatly appreciated.

 

the 3.77 isnt going to make a noticeable differance in the milage and they also come with limitedslip... i would be more then happy to trade with u for my 355 tho if got a truck with the 3.77!!

 

I do not think it will make much difference. Frankly, do not know why they offer the 2 so close. I have the 3.55 in my truck, 3.73 in my Expedition.

 

I have an 02 supercrew FX4 with 3.55ls I wish I had 3.73. I terms of gas not significant. If you are going to put larger tires are your truck go with the 3.73. RPM change is about 150 higher between the 3.55 and the 3.73. 3.73 if you are going to go with 285/75/16 or 33's you will get better performance and you wont have to spend the $1500 dollars later to change the gears.

 

All 2003 Supercrews with 17" wheels came with 3.73 rear end standard. LSD was optional. Good luck finding one w/ 16" wheels.

I had 3.73 in my 99 Supercab and now my 03 Screw. Wouldn't want any taller gear.

 

In the city the 3.73s would be better but on the highway there will be no difference on fuel mileage. 3.73 is the perfect all around gear.

 

Thanks for the info guys. It's an '03 Lariat so, it must have 17" rims with the 3.73. This is more truck than I had in mind (budget) but hey, I'll take all the goodies!! Are 245's stock? If so, I'll go with 265's or 285's when the time comes. The stock tires are so dinky. How big can you go without a lift or hitting the wheel well?
Now I'm confusing myself...and probably you too! I want to go taller, so maybe 75's, or a freckle wider and taller!! Yeah baby!

 

If its a 4x4 you can fit 285s without modifications.
Im not sure what the stock tire size is, but you can look on the driver's side door jamb, it will have it there on that sticker

 

I hate to offer a different opinion, and I know that I will be talking about a car, but I have had mustang 5.0's with 2.73, 3.27, and 3.73 gears. Quite frankly, even though I like the 3.73, I liked the 2.73 best. (all of these cars were 5 speeds) They called it the highway milage gears, but I found that with a stick you could run about 107 in third. After then driving a 3.73 geared car, it felt to me like it ran out of breath. And my 97 F-150 was 3.73 and it felt like to me it shifted to fast. So I can understand your particular search for the 3.55

 

No doubt, go with the 3.73's, especially if you want a larger tire.
Most 4x4's came with 255/70-16's (30 inches tall) or 265/70-17's (32 inches tall).

 

But Mustangs have 25" dia tires and trucks have 30-32" tires. No Suerpcrew owner would put up with 2.73 rear end, nor would you with your Nav.

 

Wow, I really appreciate your help. I love this forum and I don't even own a truck yet. Your comments have opened up a lot more options to me. Specifically 2 that are nearby, both 4X4's, the '03 Lariat 5.4/3.73 I mentioned, again pretty sure that has 17's as well as an '03 XLT 5.4/3.73 not sure if it has 16's or 17's. A couple more newbie questions and I'll go visit the dealers, BGA, you mentioned possibly spending $1500 to regear due to larger tires, you lost me, was that in reference to bringing a 3.55 up to something that worked better with larger tires? Wandell, your comments really helped too. Someone mentioned 285's as being the largest you could go with stock suspension, isn't 285 the width? 70 or 75 being the % of width the tire is high? Or am I getting that backwards? Anyway, I'm looking for a translation in to inches, what is the max height in inches you can go stock? I'm thinking I read somewhere on one of these threads that was 33. What do you recommend? With either truck, I will be shopping for tires not long after buying given the miles on them now.

 

I have 3.55 on my truck running 285/75/16 BFGs (32.9") that is the largest tire I can fit stock. 3.55 are "okay" but I would rather have 3.73 running this tire. To regear gear my truck from 3.55 to 3.73 would would cost me approx. $1500.

 

You can fit 315/70R17 on stock wheels on stock 97-03 4x4 F-150's, but I don't recommend it w/o gear swap.

RufRider, 285 is the section width in milimeters and 70 would be the percentage of sidewall height to that section width. So, 285 * 0.70 = 199.5mm high. There are two sidewalls on the diameter of a tire (top and bottom for example), so that makes it 399 milimeters of rubber. Divide by 25.4mm/in to get 15.7" of tire plus the rim of 17" = 32.7" diameter tire, ~33".

Out of curiosity, what price range are these dealers listing these 03 Screws and what part of the country? I'm considering selling my 03 Lariat.

 

Thanks for the info APT. I am using www.autotrader.com using Cincinnati, 45202 zip, with a 100 mile radius. This picks up Dayton, Columbus, Indianapolis, Louisville, & Lexington. Lariat 4X4's with 25K - 35K mis. are asking $25K-$26K at dealerships. This is higher than I want to go so will probably end up with an XLT which is perfectly fine. One of the Lariats I really like but, it depends on how low the dealer is willing to go. I'm trying to stay with '03 because that was the last year for a good long running design. By then it would seem that all the build kinks etc. were worked out...including the machine gun spark plug issue!!
BGA thanks for the clarification. So with those tires on a 3.55 axle, how are your mpg's? On one of these threads someone mentioned the same set up was returning 12-13 city but 20-22 hwy. Obviously, I'm wondering what the same set up on a 3.73 would do, sounds like little or no difference. Also, what about RPM's, it is my understanding (will test drive this weekend) that the 5.4/3.55 turns about 1900 at 70mph. Is that close to accurate? Thanks for your input guys.