mrad,

Here's my experiences...and BTW they are very similar to those that have responded already...however I have the benefit of towing with both 3.73's and 4.30's.

BTW...No V10 Ex ever got 4.10's stock. The 5.4L V8 got either 3.73's or 4.10's but V10's only came with 3.73's or 4.30's.

Regardless of gear choice...the KEY to successful towing and pulling grades without a downshift or two is DO NOT BABY THE V10...she LOVES and I repeat LOVES the RPM range of 3000 to 3200. If you can select a gear and speed to maintain the RPMs in that range...you will very likely NOT downshift. Try and 'baby' her for mpgs...and you WILL downshift...no questions asked. I've logged over 18,000 miles in three summers TOWING with my V10 Ex...so I've tried it all...driving for mpg's and slowing down if you will causes you to lose the power band even with 4.30's very easily...driving 65mph means much fewer downshifts even at altitudes approaching 8000'...

Okay...you asked a couple of questions. MPG's being one of them as well as gearing with a 6500# TT and a heavier 9000# TT. Well you are in luck in that I have towed a 7500# TT with 3.73's and now tow a 9000# TT with 4.30's.

Having towed our previous 7500# TT from Indiana to Wyoming thru the Black Hills, Big Horns and Rockies and back with 3.73's...it obviously CAN be done with 3.73's. The key that I found with that gear is to simply lock out OD and run in 3rd gear. At ~62-64mph you will turn ~2600rpms...the Ex pulls great at that rpm for most all hills...not mountains...hills.

Where I ran into some real thinking time with the 3.73's was when I was crossing the Big Horns and approaching 10,000'. I was doing great pulling 6% grades up the mountain...until I ran up behind a blue hair in a honda civic that couldn't maintain 40mph in that anemic vehicle...so my 50mph quickly sank to under 40mph and continued to slide backwards. The problem is that we only have a 4spd trans and one of those is OD...the other issue is that 1st and 2nd are spaced WAY far apart from each other. I found that if I ran up the rpms in 1st and let the tranny shift to 2nd...it would bog due to the weight, altitude and grade...so I had to be smarter than the auto trans...I manually shifted into 1st and held her there until just before the rev limiter (5200rpms) and then shifted into 2nd...and when it hit 2nd...it was in a good spot rpm wise to continue to gain speed and pull the hill. That civic, while frustrating at the time, helped me to figure out some capabilities of the Ex at altitude on a steep grade...

So the 3.73's have their limits with 7500#'s unless you are willing to experiment like I did...but to be honest...how many 10,000' climbs are you going to make and how many blue hairs in civics are going to shed your mometum?...but now you know how to regain it if it happens to you!

Okay...mpgs...I log each and every mile and track each and every gallon I pump. I go by AVERAGE mpgs and NOT one tank wonders. When I had 3.73's I pulled slightly over 7,000 miles that first summer. I AVERAGED 7.8mpgs in all those miles.

The funny thing about mpgs is that as others have pointed out...WIND plays a HUGE factor in what you get on a trip...fight a 30mph head wind...and I don't care what you are driving...if you are pulling a brick behind you...mpgs will TANK...remember too...my TT has slides...both did...so they are 11' tall to the top of the A/C unit...lower wind profile TT's WILL do better...

A couple of years ago I purchased our current 9000# TT. Given the experience I had in the Rockies with the 7500# TT and given the fact that I knew I would be headed back to the Rockies soon (which I did this past summer)...I knew I wanted deeper gearing so I swapped mine to 4.30's.

In the last two summers I have traveled around 11,000 miles including the Appalachians, Smokies, Sandia's, countless peaks in Utah and then Vail (10,600') and Loveland (11,200') in the Rockies...the V10 did great.

AVERAGE mpgs' actually went up slightly to 8.2mpgs. I suspect it is due to the fact that I can acutally run OD with the 4.30's where before I had to lock out OD and run 3rd. So my overall rpms are actually lower with the 4.30's and I have fewer downshifts.

That AVERAGE mpg also includes 1800 miles from this summer when I was fighting a fierce 30+ mph head/cross wind when towing to the grand canyon. Depending on the wander in the highway...it was a head or cross wind for 4 days...

I can tell you that I can almost set my fill ups by 8mpg...it is that consistent. Sure there are tanks lower and tanks higher...and you will know what you are getting based on tail or headwinds. I've had as high as 10+ and as low as 6...but speed, weather, wind, terrain ALL play a role...that is why I choose to report the AVERAGE I have recorded over 18,000 miles of towing and it is a solid 8mpg with both 3.73's and 4.30's. Notice that my 8mpg with 4.30's is with a TT that tips the scales at 1500# MORE!!!

If you are thinking about a 9000# TT and plan to travel to areas like the Rockies and southern Utah...I'd highly recommend 4.30's. The seemingly constant 8000' elevations with a normally aspirated engine zaps power to boot...you don't need to handicap her with improper gearing as well...

But if you don't plan on tackling those tall peaks in the west...3.73's with OD locked out should work well enough with 9000#'s.

I hope my long winded answer helps some.

If not let me know.

Joe.