Recently pulled 6500# camper to smilies and back from Northern Indiana. The first 180 miles I did not use overdrive and got 6.9 mpg. I used overdrive the rest ove the trip and got 8.3-8.9 the rest f the way. Flying down hills and crawling up them... V10 w/ 3.73 rear.

 

As The "Unquestioned V10 Tow Master" (Tom) will soon advise, tow in Overdrive and let the V10 rev. That's what it loves to do and it will pull like no tomorrow doing it.

If you REALLY want to kick things up a peg, some 4.30 gears will really wake it up. Joe aka X_Hemi_Guy and the former "Unquestioned V10 Tow Master", had a 2005 Excursion that was equipped with 3.73 gears. He too towed all over Indiana and This Great Country and after a summer of towing, opted for 4.30 gears front and rear. He was VERY pleased with the difference and if you search his threads, you'll see that I speak the truth.

Prior to Apocalypse getting his 2004 Excursion, it was in my possession until the transport company came to get it. He had 4.30 gears and that.thing.moved.

Whether you opt for the 4.30 gears or not, let it rev and take you for a ride.

(yes, I am a diesel guy speaking highly of the V10, lol)

 

I get 7.8 towing my 11.5ft tall 9200lb loaded TT! But yes Tom will be by to give more in depth info.

 

Thanks guys, you are making me blush! .
Rich, I had a similar experience back when our EX was still turning 3.73 gears, stronger towing performance with OD locked out but poor economy doing it.
Are you rolling on stock sized tires? That's important here as any tire taller than the factory 265/75R16s at 31.6" tall will effectively reduce the gear ratio even more below the 3.73. And that low of a ratio will not only rob the V-10 of performance because its being forced to get the job done below it best power/torque band of the RPM range but it will put more stresses on the trans than necessary.
Back when our was all factory stock we towed our 9500lb toyhauler with it on a couple of trips up/down the East coast to/from Philly and Savannah. On those trips we got 6 to 7 MPG while towing in OD and it would downshift if it ran over a shadow! And throttle response and performance were not exactly inspiring.
I had big plans to run 35"s and a little bit of lift so after some research I concluded that 4.88 gears would be what it needed to move the effective ratio to the far more towing friendly ratio of 4.30 for these motors. I got a good deal on a complete set of axles from an early EX that already had 4.88s installed, so we picked them up (it's own story) and I swapped out the rear axles housing (I do still have to the front axle one of these years.....). At the same time I also mounted a set of the '04 Lariat 18" rims with slightly taller than stock 32" tires, which worked out to about a 4.80 effective ratio. The following week we hitched up and made the same trip as earlier down toward Savannah, running the same 60/65 MPH at the same weight. We got 9.0 MPG! . And while the RPMs did increase a few hundred at highway speeds it was not screaming or even a little unpleasant. A big part of the increase was due to the fact that it didn't drop out of OD the entire trip on the highway, a huge improvement from the previous trips!
The next mod I made was to install a set of Banks headers. They didn't really improve the mileage but I feel that they did help to improve the throttle response and unleash a bit more power when climbing hills at higher throttle openings under heavy loads.
Next mod was the addition of Custom Tunes from 5Star Tuning, I got the SCT handheld tuner and 5 tunes, 87 Octane Economy, 87 Tow, 87 Performance, 89 Tow and 89 Performance. I provided 5Star with all of my rig's details and mods (as well soon to be done mods) as well as the size and weight of the trailer. After a good bit of experimentation I came to find that for my style of tow driving I preferred the Performance tunes over the Tow tunes. I felt that the Tow tunes were too aggressive in wanting to downshift on hills while the Performance tunes would allow for higher throttle openings while holding onto OD. During the time we had the tunes and were towing the TH I was still experimenting with the various tunes so we really didn't see any significant gains in MPGs then.
Next I finally upgraded to the 35" tires I had planned for earlier, now my effective ratio was 4.39, almost the same as the factory option of 4.30 that so many other users have sung the praises of. . I expected the mileage to take a small hit with the reduction in ratio on the next tow but was surprised to still pull down the same 9-ish results. I was still learning how best to make use of the Performance tunes and was now seeing the results of those lessons learned at the pump.
Soon after we upgraded to a new 41' 11,000lb travel trailer which had me back to paying very close attention as I played with the tunes to see what worked best in various situations. It also a way for me to entertain myself on long tow trips. . After a few trips to figure out the new combo we were seeing 8 to 9 MPG on our mostly highway trips and it was still holding OD very well on most Eastern Interstate Highway grades only dropping a gear if in traffic or on the few steeper and longer pulls. Through experimentation I found that the 87 Perf tune would allow for throttle openings in the low 50% range on climbs while holding OD between 60-65 MPH and would drop down at about 54-55%. The 89 Perf tune would allow for throttle openings up to 60% or a bit more before dropping out of OD in that same speed range. So now for trips on mostly flat land I'll use the 87 tune and buy that cheaper gas while trips through the mountains I'll run the 89 tune and burn the mid grade gas. So far our best trip mileage was last July coming home to the Philly burbs from Niagara Falls where ran the 89 tune and got 9.5 MPG over that 420 miles, not too bad for a gas hog V-10 at almost 19,000lbs (and three kayaks strapped to the roof!)
After logging a fair amount of towing miles (over 30k miles) with these various combinations of trailers and mods and paying close attention and keeping a log I can say without question, that the deeper gears were the single biggest towing and performance gain I have for this EX. . I would rank the 5Star custom tunes as second and a great first choice if a regear isn't in the budget or if you are not pulling as heavy or as many miles as we are.
Back when totally stock I used to see 14-ish MPG on my daily driving mix of 50/50 highway and town miles with a best ever tank at 15.5 MPG on a highway/town mix in Maine with 6 adults onboard on a very hot day. Nowadays I no longer daily drive the EX so no data on that with the current mods but I did see 12.5 MPG on an all highway solo trip (to Savannah again!) with cruise set to 65 MPH. some of the lost MPG is from the lift and bigger tire, it's not all from the deeper gears.

(Was that enough in depth advice guys? )

 

You are very short-winded !

 

That's alot to take in...WE. Great stuff, I will soon be purchasing an EX with 82,000 miles. The reality is that we will keep this vehicle 10-15 years. In that time we will pull roughly 1500 miles a year with the exception of an upcoming trip of 4500 "Towing West". We currently have the 3.73 rear running stock tires and will still have 3.73 with the new EX.

Wondered what it could cost to swap out for the 4.30 axle parts labor ect... Wondering if it would ever pay for itself with the amount I towing we do? Thanks WE.

 

Just wanted to chime in as I got to drive Toms truck recently and it runs perfect with the gears in it, although i didn't get to tow anything I can certainly say that the power is there.
I was so impressed in fact that I REALLY REALLY want to find a set of 4.30 axles to swap under one of my trucks. Don't fear the gear!