3.42 vs. 3.73 gears.......

Depends a lot on what truck you are looking for.

Most have double overdrives, and effectively will run the diesel engine at a lower RPM than in years past, no matter what rear axle ratio you are using.

So are you looking for a 2500, 3500, single rear wheel, or dually? Or F-250 or F-350?

If you plan on graduating to a fifth wheel in the 30' length, with a 12,000 GVWR, consider it should have 20% of that weight on the hitch pin. So that would be around 2,000 pounds.

If you also have a crewcab, and plan on taking along 500 - 800 pounds of passengers, generator, some firewood, ect. then this can add up to another 200 - 500 pounds. This might require a F-350 with a 3,800 - 4,000 pound cargo rating to tow such a large fifth wheel, though a 2500 or F-250 with a cargo rating around 3,000 pounds is fine for just about any travel trailer, as even the largest are only about 11,000 GVWR, with a 1,200 - 1,400 pound hitch weight, and are not a problem for any of the modern 2500 trucks.

Best thing to pick up now is a towing guide from each of the three big truck manufactures. They discuss GVWR in length, and you can pick up a lot of information from the brochures.

It also has the GCVWR of each truck, with various rear axle ratios.

Fred.

Since your thinking about a 5th wheel go with the 1 ton, and if the 5th wheel will be over 13k gross, buy a dually. You'll never regret it.

I have heard some say "buy your second RV first". When we bought our first 5ver (used)I knew that in a few years we would want a bigger RV. I went straight to a F350 CC, PSD dually, and the only regret was not getting a 4X4, not so much for the RV but for snow and mud. because it is my daily driver.

Moved from Forum Technical Support

I seriously doubt you'll find a diesel truck that offers a rear diff lower than 3.73 to begin with.

Happy camping!!! See y'all down the road!!!:)

In reality i doubt you will see much difference between the two in non towing MPG. It sort of depends on what truck you thing you will get. The V8 diesels dont start making power until much higher RPM. Thats one reason GM only offers the 3.73. The 3.4 ratios are for economy and with the double OD transmissions now days it is hard to justify anything other than those two.
But!!! My dually has 4.10 rear end ratio and I have a hard time thinking anything different would help me. I have seen as high as 12.5 towing across the high desert of SE Oregon pulling 13,500 pounds. Same truck traveling between Lakeview and Klamath Falls I got 18.5 hand calculated unloaded. And that is not the flat lands of the Iowa. With my truck I can run all day with the cruise control on. Something I have doubts I could do with a 3.42 rear end. At the end of the day you have to make the best educated guess you can. Basing it on what percent of the time and where you are towing VS non towing. Where you are located, personally I think I would pass on the 3.42 and go at minimum 3.73.

It looks like you've got 3.73 now. Are you happy? If so stick with it, especially if you want a heavier trailer.
Are you looking at a Chevy? They don't offer any choices; it's 3.73 and that's it.
If you're looking at another Dodge I'd keep what you have if you're happy.
Ford's, I don't know.

crickeydog wrote:
I seriously doubt you'll find a diesel truck that offers a rear diff lower than 3.73 to begin with.

Happy camping!!! See y'all down the road!!!:)

2013 Ford 6.7 can be ordered with 3.3, 3.55, 3.73 and 4.3 depending on model and GVW.

IMO a new diesel truck is a '13 model.

If you choose a 2500/3500 SRW Ram with the Cummins you get a 3.42 only which can tow up to 17xxx lbs depending on truck configuration. If you want a 3.73 or the 4.10 gears you will have to move up to the 3500 DRW that has up to a 30000 lb tow rating.

With the GM and the Dmax/A you get a 3.73 only for up to a 22300 lb tow rating depending on truck configuration.

The F250/F350 SRW Ford has up to a 16700 lb tow rating with a 3.31 and 3.55 axle ratio. If you want a 3.73 or the 4.30 gears you will have to move up to the F350 DRW which can tow up to 24500 lbs.

If you choose a 2500/3500 SRW Ram with the Cummins you get a 3.42 only which can tow up to 17xxx lbs depending on truck configuration. If you want a 3.73 or the 4.10 gears you will have to move up to the 3500 DRW that has up to a 30000 lb tow rating.

With the GM and the Dmax/A you get a 3.73 only for up to a 22300 lb tow rating depending on truck configuration.

The F250/F350 SRW Ford has up to a 16700 lb tow rating with a 3.31 and 3.55 axle ratio. If you want a 3.73 or the 4.30 gears you will have to move up to the F350 DRW which can tow up to 24500 lbs

This is the correct answer if looking at a new truck.

I am looking at Ram's and I wouldn't go with the 3.42 for even part time towing. If you go to the Diesel Forums (dieseltruckresource.com, dieselbombers.com) you will get more info on this decision.