5r55e in 5.4 Expedition? 3.27 or 3.08 gearing? Getting better mpg?

[452films]

Hey everyone, I'm new to Expeditions, but not new to SUV's. My last car was an 03' Durango 4.7, and before that a 99' Explorer 4.0. I'm picking up a new SUV next month and really want an expedition. I've found EXTREMELY clean expeditions with bad trannys for under $800 ( Found an 00' 5.4 Eddie Bauer edition with a bad tranny and 110k on it for $800 obo, super clean ) and I would like some more gears as well as a longer overall gear ratio. I'm not familiar with changing gearing on a 4x4.

Now my questions.

Is the 5r55e from the explorer a straight swap for the stock Expedition tranny? Will it hold it up the 5.4 2v? Is there a 5 or 6 speed tranny that will bolt in place if not? I'm also looking for something that will be durable as I'm not exactly easy on my stuff ( I enjoy doing some trailing and a very little bit of mud, but overall drive a lot. Average about 600 miles a week, and 800 a week in the summer )

I want to change the gearing as well to squeeze a few more MPG out of it, and get a little more top end out of it. Im a junior in high school and half of my school day I work on cars but usually don't get into things like diffs. How much are the parts I need and what do I need to go from the stock 3.55's, to 3.27's? Is 3.08 to long for an expedition that will be occasionally going on trails? Biggest tire I plan on running is a 285/70/17 ( I have 17's from an F150 I had ), and I don't use that aggressive of tread tires ( just your basic AT ).

I'm also looking to get more out of it MPG as well as making it run a little smoother. Will a more free flowing exhaust free up some MPG. Better flowing cats and a more straight through design for a muffler ( magnaflow possibly ). Is it a myth or fact that a cold air intake will free up some MPG as well? Any other things with this to get some more MPG.

 

[Racenut]

Well for starters the 2000 - 2002 Expeditions with the 5.4L run the 4r100 trans, which is a great trans ( the same trans also backs the 7.3l powerstroke) as for a 5 speed auto swap you will more than likley run into computer issues since they have a completly different shift stratagy.

As far as gearing if you get into that tall of a gear your Expy is going to be a DOOOOGGGGG off the line and you will really have no low end TQ to speak of. I would start by doing the exhaust with a rear cat delete and get rid of the factory Y run two pipes into a DI/SO or a DI/DO free flowing muffler. Then do the GOTTS mod (there are a few write ups on that hear in the forum just use the search) then I would do a programmer I run the Edge CS and it makes a world of difference (also if you do decide to do gears latter on you can adjust the gear ratios and also tire size so that your speedo will function properly).

The biggest thing to get "good" milage out of an Expy is to keep your foot out of it. I know it is hard to do especially after the exhaust work and programer but in all reality that is the only way you will pick up milage numbers.

Here are a couple of pics of my exhaust for ya! I do not have any pics of the rear cat delete yet, but it made a huge difference in the top end, also if the resonator at the tail pipe has not been removed yet make sure to get rid of that as well.

If you can land it for $800 it sounds like a hell of a deal so post some pics when you get it.

BTW - Just for FYI make sure to have a good helper when you do the trans TRUST ME it is a heavy SOB!

 

[Racenut]

Also mine is a '02 2wd with 3.55's and after all the exhaust work and programmer if I can keep my foot out of it I'm pushin 19-20 mpg interstate driving at 80 mph. Yours would be a bit lower due to it being 4wd but you don't buy a 5,000 + # vehicle for gas milage!

 

[tonydiv]

I couldn't have said it better myself.

If it's a '00 5.4l 4x4 it probably has 3.73 gears in it. Keep them as they are.
Because of my oversized tires, my truck has the apparent gear ratio of approx. 3.08. Which makes it a bit slow off the line. Although I have more 'top end", mileage on the highway isn't what you would expect it to be. The motor just plain has to work too hard to turn those tires. When you have too high of a gear (lower numerically) it feels like you're always towing a trailer behind you.

I plan to put in gears this summer in the 4..27 to 4.56 range (haven't decided yet) to make the truck 'think' it has 3.73s in it. This should net me 3 to 5 mpg minimum.