Hello,

I have a 2000 6.8L V10 Ex (4x4) with a 5" lift, 37" Nitto Mud Grapplers, and a 5star tune. Currently it gets around 8.5 MPG, and when I am driving on the freeway, it seems to frequently shift in and out of overdrive (mostly when going up hills). I assume it has the stock 3.73 gear ratio, but I cant be 100% sure (the sticker is blank in the axle ratio area). From how lethargic it is during acceleration, I am fairly sure it is 3.73.

For me, the Ex is mostly a winter vehicle, and for when I need to haul a lot of people or tow something (but the towing is fairly rare).

From what I have read on these forums, either 4.30 or 4.88 gears sound like the best options for my 37" tires.

My question is, would 4.30 gears be the best option if my primary concern is freeway driving (without the constant shifting in and out of OD) and MPG? (and before you ask, I did not put the 37" tires on, but they look bad ***, so I shall keep them. I just want to squeeze as much MPG as I can out of this beast in its current form)

Or should I go with 4.88s? Sticking with the 3.73's is also an option if the 4.30's or 4.88s will only drop the MPG (but I feel like constantly having to push the pedal to the floor just to get this beast to move is chipping away at the MPG I could get at a more stock-ish gear ratio)

Any input is appreciated.

 

4.30 ratio for a stock 31-32" tire. I would go a minimum of 4.88

4.56 will get you close to a 3.73 effective, 4.88 near a 4.10 and. 5.13 will be an effective 4.30 with an OEM tire size of 32". I used the calculator below.

4Lo.com :: Tire Size Change, New Gear Ratio Calculator

 

ok, here's some.... I have heard guys say to get the higher ratio as the bigger tires lower the effective ratio...

oops took too long to respond!

 

My opinion based on having used my EX with 3 different effective gear ratios (3.73, 4.80 & 4.39)..........go with 5.13s.
Changing gears is fairly expensive, so in my mind doing right and doing it once is important.
You mentioned the lethargic current performance, there isn't much fun in driving a dog, so if you are going to drop the coin on gears, make it well worth the cost with some decent performance and improved economy!
Like Coop said, 5.13s will get you to an effective 4.30-ish ratio, a very good place to be with the rev happy V-10. My EX with 4.88s and 35"s has an effective 4.39 ratio and it enjoys very nice solo driving performance and great towing power (11,000lb TT).
If your rig does have the common 3.73 gears then you are spinning an (painfully less than) effective 3.18 ratio. That would have your engine lugging a lot and it's putting additional stress on the transmission.
Going from that combo to a 4.30-ish via 5.13 gears should actually improve your mileage, maybe not up to Prius levels but it should increase from the current 8.5 MPG. Don't forget that the big tires and lift also rob some economy just due to the addition rotational mass and aero drag, but I would think getting the ratio up to 4.30-ish should get you up to 11/12-ish on the highway and not much worst around town. Deeper gear ratios are a real plus for city driving in a heavy vehicle, much easier to get the weight moving. With my setup it gets 12.5 MPG on pure Interstate Highway trips with the cruise set at 65/68 MPH, and towing that 11k TT I'm beating your current 8.5 MPG on most trips with 8 to 9 MPG and a best yet of 9.4.
If for whatever reason you don't want to go that deep, then go with at least 4.88 gears.

 

I too agree 5.13 would be the way to go.

Just be aware the transfer case has a 2.6 ish low range reduction. So the multiplier is exponential not linear.

Your low range with 5.13's will be neck breaking and could easily damage things.

Not sure this is right but low range equivilant gear ratio would be 9.7:1 for 3.73 gears, and 13.3:1 for 5.13's.

Basically your 2H and 4H wI'll be close to factory 4.30 gears with 37" tires, but you 4L will be wayyyy lower than factory 4L.

 

5.13 and don't look back.

 

So 5.13 sounds like the way to go.

My dad has a hydraulic lift and all the necessary tools, so I think we can manage the install ourselves, though I have never done a gear swap before.

What needs to be replaced? is it just the ring an pinion gears that need to change?

At the moment, I'm looking at buying these gears:


https://www.amazon.com/USA-Standard-Gear-F10-25-513L-Differential/dp/B0078U9T98/ref=au_as_r?_encoding=UTF8&Make=Ford%7C54&Model=Ex cursion%7C661&Year=2000%7C2000&ie=UTF8&n=15684181& newVehicle=1&s=automotive&vehicleId=1&vehicleType= automotive

and a new gasket. Are there any other parts that I'll need for the swap?

 

Carrier and pinion bearings MAY need to be replaced. I think Moog or Timken makes kits with everything you need.

 

A full install kit front and rear is recommended.



Unless your cheap like me, and have done a lot of them, and can tell when the bearings are questionable or not.

 

Hm...that brings up another question:

If I swap out the rear gears for 5.13, do I also have to swap out the front gears as well? What would happen if I ran the 4x4 with a different set of gear ratios?

 

I found this 5.13 kit:

F250 F350 Ford 10 25" Dana 60 5 13 Ring and Pinion Master Install Gear Pkg | eBay

Opinions? Is the front of the excursion a "Dana 60"?

 

The EX front axle is a Dana 50, it shares a lot of parts with the 60 but I'm not sure if that includes the gears.
Yes, you do need to regear both front and rear diffs together to the same ratio, with different ratios a four wheel drive event that has any decent traction will bind up, potentially enough to find the weakest link.

 

Yep. And you'll be quickly back in 2wd if you're lucky.

 

The stuff in the pumpkin is different between the D50 and D60. You need the D50 stuff.

Also, yes, the front gear change is required, unless your not going to ever use 4x4. It will bind up, and hopefully, just stops the vehicle, or break parts.

 

So I think I have decided on this for the rear:

1993 2006 Ford 10 25" 10 5" 5 13 Ring and Pinion Master Install Gear Pkg | eBay

For the front however, I'm not sure which Dana 50 the Ex has. Whats the difference between "Straight axle" and non-straight axle?

http://www.ebay.com/itm/1998-2002-DANA-50-STRAIGHT-AXLE-5-13-RING-AND-PINION-MINI-INSTALL-GEAR-PKG-/331742312184?vxp=mtr&hash=item4d3d61f6f8
http://www.ebay.com/itm/1998-2002-FORD-DANA-50-5-13-RING-AND-PINION-YUKON-GEAR-MASTER-INSTALL-PKG-/331742275824?vxp=mtr&hash=item4d3d6168f0
Are those two actually the same thing (aside from gear brand and gasket, which I assume accounts for the price difference)?