Thread Tools Search this Thread Display Modes
Old 11-19-2012, 05:24 AM   #15
Rivet Master
jdalrymple's Avatar

2009 27' FB Flying Cloud
1991 35' Airstream 350
Siloam Springs , Arkansas
Join Date: Oct 2006
Posts: 1,491
I have towed with 2 Duramax trucks, and loved them both. Both rear-end gears were 3.73.

The major difference is the transmisson in the '12 is a six speed. That brings the cruise RPM down to around 1800 at 70 mph.

I do hate the DEF issue, but I guess the folks at the EPA like having all the air scrubbers driving around. So we can have more iceburgs, of course.



Jeff & Cindy
Hunter RIP

'09 27FB Flying Cloud
'91 350 LE MH
jdalrymple is offline   Reply With Quote
Old 11-25-2012, 10:25 PM   #16
Vintage Kin
slowmover's Avatar
Corpus Christi , Texas
Join Date: Nov 2006
Posts: 6,302
Images: 1
I wouldn't sweat 3.31. I intend to change my 3.73 manual transmission DODGE to 3.42. I don't mind going a bit slower from a stop or on ascents, and the gear ratios would allow me to otherwise (solo) to stay closer to peak torque in most situations (better mpg).

These trucks are all over-powered. Mine as much as yours despite the differences when it comes to pulling any size A/S.

Put your reading, instead, to a PRO PRIDE hitch and TT disc brake conversion.


1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 10-cpm solo, 18-cpm towing
Sold: Silver Streak Model 3411
slowmover is offline   Reply With Quote
Old 11-28-2012, 08:04 PM   #17
Rivet Master
pappy19's Avatar

2002 30' Classic S/O
Garden Valley , Idaho
Join Date: Jul 2010
Posts: 1,256
3.73 all the way. I would have a 4.10 if they offered it but they don't. Most come with a 3.55 but you can find a 3.73 if you look hard. Ford wants more higher rear end ratios as it shows up better on their emissions(lower the number, the higher the ratio). Mileage is a wash between the 3.73 and the 3.55. Higher than that and you loose power but gain mileage, but also more strain on the tranny. Your choice.

2008 F-250 4X4 Lariat V-10
2002 Airstream Classic 30' w/SO #2074
2007 Kubota 900 RTV
1996 Ford Bronco
2007 Lincoln LT
pappy19 is offline   Reply With Quote
Old 11-28-2012, 10:00 PM   #18
Rivet Master
mefly2's Avatar
2015 25' FB Eddie Bauer
Western , ** Big Sky Country ** Montana
Join Date: Feb 2010
Posts: 2,212
3.73 in our diesel and the AS disappears in the mirror ...
~~~~~~ mefly2 ~~~~~>>>
AIR 44105 /WBCCI - formerly 2015-1; Yamaha XT250
:>) ducts are now in a row w / 2015 ducted air :>)
* 2015 Duramax 2500 Diesel * Honda EU3000iS
<>2015 International LE Eddie Bauer FB25<>
mefly2 is offline   Reply With Quote
Old 12-09-2012, 03:33 PM   #19
Rivet Master
dbj216's Avatar

1986 34' Limited
1966 24' Tradewind
Conifer , Colorado
Join Date: Jun 2009
Posts: 2,522
3.31 with18" wheels versus 3.55 with 20" wheels

I thank you Airstream truckers for your descriptions of your experience. I did some thinking on this axle ratio business. Tire Rack has a great website that gives tire size diameters. 275/70R18 tires are 33.2 inch diameter resulting in 627 revolutions to travel a mile, 275/65R20 tires are 34.1 inch diameter resulting in 610 revolutions per mile. The Super Duty transmission top gear is .67 to 1 overdrive. So 3.31 axle ratio results in a 2.21 overall ratio, and 3.55 axle results in 2.38 overall ratio.

The 3.31 gears with 18 inch wheels gives 1386 engine rpm at 60, and 3.55 gears with 20 inch wheels gives 1452 rpm at 60.

Diesels don't have throttles. I probably have to feed the same fuel at 1386 rpm as I would at 1452 rpm to maintain 60 with the Airstream behind me.

I think I am fussing about nothing. Either combination would result in the same performance.

dbj216 is offline   Reply With Quote
Old 12-09-2012, 06:20 PM   #20
4 Rivet Member
elolson's Avatar
2000 34' Excella
Tucson , Arizona
Join Date: Apr 2006
Posts: 375
Dude I read the posts. No one mentioned that the new 2012 Ford diesels are spec'd at *800 ft-lbs* and 400hp. That is way over the top of what they have been the last few years. Airstreams are light in the big picture of 40' 5th wheels etc and the other junk people tow. Get some nice tall gears and enjoy the fuel mileage and cruising along. I have a 34' excella and had a Dodge cummins 3.73 with the factory 600ft-lbs. That towed just fine all conditions. I now have an '02 7.3 ford (550 ft-lbs with a standard) with 4.10 gears. It also tows fine and I wish I had 3.55s.

elolson is offline   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Virginia Campgrounds

Reviews provided by

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 11:32 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.