What gears are in it?

I get 10 around town and 16 max on the highway with 3.73s, no lift, and highway tires on a 2 valve 5.4L.

 

I had a 2000 with the 2 valve is 10.5-11 was my normal average empty.

 

It has 3.73s and my 35s. I have my sct live wire ts set on economy tune as well.

I just find it odd that it doesn't do a little better. My dad's 2000 expedition with a 5.4 gets 17 on the highway and 14 to 15 in town. I know they are two totally different rigs, but I still thought it would do better

 

I'd venture to say that the 3.73s with 35s are hurting you. That's a much heavier tire. Your truck will also have more drag because of the size difference. Do you have a tonneau? My fiberglass one makes a huge difference on the highway.... about 2 mpg

 

Yes I do have a tonnue cover. I figured with the tuner, the air raid intake, and the exhaust, it would have helped out a bit on the mpgs but I haven't noticed a changes at all

 

I really hope I can improve it somehow with out dropping the 35s. Regearing would only raise the rpms at cruising speeds right?

 

Changing the gear ratios has an affect at all speeds. It is probably more noticeable at cruise speeds because of the duration of time that you are at that speed.

 

4.56 gear would put you above the effective ratio of the factory, give you a bit more pep and probably some mileage. 4.88 ratio would give you an effective ratio of 4.39 which 4.30 is what the modular engines like.

Build is looking good.

 

So I noticed my truck started pinging a,bit the other day,and ran codes and these came up, any idea what's going on? I returned the truck to stock and everything seems ok for now. It was on my economy tune




Also I had a thought on my poor mpgs, could it be possible my throttle body needs to be cleaned? I read something a while ago that the 5.4s need their thottle body's cleaned once and a while

 

Pulled these off another forum google search.

 

So how should I go about diagnosing it further? I'm betting the computer is messed up as ford forgot to re connect the grounds on the main harness when they were working on it. And they agreed that if a problem came up down the road they would fix/ replace it if a problem came up

 

Take it to them for warranty work and see what they say.

 

Clear the codes first and see what comes back.

 

Did that already David and they are back

 

I would take it to the dealer and let them handle it. If they fix it and something else goes wrong then it is on their tab as well. If you do any work or have someone else do the work then you have given them a way out.