Hey all! Periodic lurker, first time poster here.

I have a 2000 Excursion 2WD with the 7.3 Powerstroke, S&B Cold Air Intake and an Edge Evolution CTS2 tuner. I daily drive it on the "Extreme" tune and can get about 20mpg on the highway, but I'd love to improve my fuel efficiency.

Has anybody swapped to a taller rear end ratio to get better fuel mileage? Anything out there that would also give me limited slip? It seems like the factory rear end is an open diff.

I'd love suggestions. Glad to finally be part of the forum!

 

The Eaton Tru Trac is the limited slip I would use if I didnt want a locker.

improving the Ex mpg….. lower it 6" and chop the top 12". in other words you will need to radically decrease the aerodynamics of the brick to get meaniful MPG improvment.

or just take your tuner off "Extreme" setting as making Extreme power requires extreme fuel. ( ok ok…takes as much fuel as your stock injectors can deliver )

 

Your getting 20 MPG out of a 7000 pound vehicle, I'd leave it the way it is. You could see if a Detroit Truetrac is available for your truck. They are supposed to have good street manners and they don't have clutches to wear out.

 

Eaton is Detroit and yes they make a TruTrac for the 10.5 sterling

 

I think we were typing replies at the same time. LOL

 

When your giving it full throttle yes, but higher hp tunes also increase the injection timing, which increases fuel efficiency. I have always gotten the best fuel mileage in my highest hp tunes, as long as I was driving it like I wanted to get good fuel mileage.

 

Welcome to the EX forum!

The EX is a big non-aero brick but any aero improvements you can make will help with your MPG quest. I'm a hyper-miler in my '94 Geo Metro and have seen some decent MPG gains from a few simple aero improvements and taller tires.
A cheaper alternative to a gear change to at least test to see if it improves your mileage would be to run a set of taller rear tires to simulate a numerically lower gear ratio. Trading your stock 31.6" tires for a set of 35"s will reduce the effective ratio by about 12%, so with your 3.73 it would be an effective 3.30-ish ratio. On my little car I am rolling on 7% taller tires but looking for 14" 4X114.3 steel wheels to go to a 10% taller tire.
What style side mirrors do you have? The smaller paddle mirrors will be more aero than the larger two armed towing mirrors.
Have you tried running a lower front air dam? Either a late model SD 4X4 version or a custom setup. I used racecar flexible plastic sheeting and aluminum angle to fabricate the air dam on the metro, it has about 4" of clearance from the ground, it does scrape a bit on some driveway aprons but the plastic has plenty of give to it. You would need to measure and test to see how far you could push it on the EX.
What style tires do you have on the EX? A highway rib style tire will give better mileage on average than an All Terrain tread. What pressures do you run in the tires? Slightly elevated pressures can help improve mileage at the expense of ride comfort.
Do you still have the factory roof rack cross bars on the EX? If you don't use them removing them should help to clean up the aero a whisker and save your roof paint from the bars rubbing.

 

Hey all, I really appreciate the replies! I just started a new job a few weeks ago, so I got totally swamped after my initial post and I'm just now getting back to this.

1. I've always been under the impression that driving "normally" with an aggressive diesel tune yields the best MPG. So far that's what I've observed in the real world vs. stock tune, although I haven't tried going one step down on the tune and testing it.
2. Sounds like a Detroit Truetrac is the consensus for a limited slip with reasonable smoothness. From what I understand it's the ring and pinion that determine the ratio though, correct? So I'd have to swap that out?
3. I really like the idea of trying out some taller tires to "test" the axle ratio theory. Good call! I should be able to correct the speedometer with my tuner. I'll have to dig in and see if it has parameters for that.

Has anybody else gone to a limited slip on a 2WD Excursion? Is it helpful in the real world? If I don't have weight in the back end of this truck, it'll get stuck on slightly damp grass and an incline, especially with my highway tires.

 

I do run highway tires, as I regard a 2WD EX as more of a road tractor than anything else. I keep them at 80psi rear and 70psi front. I care more about my wallet than my ride quality!

 

Ring/Pinion/Truetrac install is in excess of $2k.

So, what mpg gain are you looking for...2mpg, 5 mpg? You can subsidize a couple mpg on $2k

 

2K? Labor must be really high where your at.

 

Break the parts down.

R/P = $400
Locker = $650?
Carrier bearings = $70
Shim kit =$30
Marking paste = $20
Lube = $20

Gotta pull the front axles on a D60 or D50. So now you have the big hub seals that are $25 each

Then as long as he is in the front, inner axle shaft seal, those are like $12 each.

Local driveline guy quoted me $600 labor. I'm doing it myself.

edit: It may not be in excess of $2k.....but it's within shouting distance.

 

It's 2wd so he's only doing the rear. You can get a ring and pinion, install kit, and Truetrac for the Ford 10.5 for $1000. Labor for one axle shouldn't be more than 400.

 

I'm doing my front....had that on my mind. Sorry.

 

Thanks for that info, guys! Yeah, it may not be worth the trouble for a few MPG. I think I might go the route of taller tires, if only to test the theory.

However that limited slip does sound nice. I have to think it would help me in the few instances that I'm on slick surfaces.