I'm with you on the combined milage way, that is why I was proposing the this way to get a more apples to apples comparison between the gear ratios. At the end of a tank, if we could get the Average MPH and the MPGs then we could do a combined comparison.

 

I have an 09 Laramie QC 4X4 with the 3.92. I am averaging 20-21 mpg's on the highway and 12-13 mpg's in the city. Mind you I tend to hit the gas a little more in the city just to hear my Magnflow. The highway driving is on a very straight road with very few hills and the cruise control on. Average speed around 75 mph

 

Just get the 3.92's, you get the benefit of an lsd and the extra performance, and the fuel mileage won't be much different. The 3.21 equipped truck is dog slow off the line. Honestly, don't expect to win a drag race against even a civic until you're over 30mph. And it's crap for towing, the truck never wants to get into top gear.

Most of my driving is towing a small utility trailer, maybe 2500lbs total, in town. I know this is a bad combination for mpg but with the 3.21's I only get in the high 9's. I feel this is unacceptable as the '08 Titan I had pulling the same load regularly got 13-14mpg.

 

I have 09 hemi with 3.92, I live in somewhat hilly mtns in NC but nothing too serious. For 1500 miles with about 50/50 city/highway I averaged 13.78 combined. In city it was about 12.3. I did not drive aggressive. The truck is totally stock with 19,000 miles and is a Laramie that weighs 5810 lbs without a driver. It has a tonneau cover and side rails and nothing else except all Laramie options plus a few others.

 

I have a 2010 QC 4WD BigHorn with 3.55's my combined is 15.2 MPG with 60/40 Highway/City. The truck only has 1,340 miles so it's still breaking in.

 

Don't know of a better way to show you other than this:



That's like 80% city driving with 3.92's.

 

I'm doing the switch next week from 3.21s to 3.92s. Right now I get 14.8-15.5 in the city and 21.8-22.5 on the highway (@ 68-70mph)

 

My mileage is similar, I'm afraid to swap to 3.92's because Ill probably get a ticket. Thie Laramie/3.21 ratio is plenty quick for me once it rolls through 15MPH.

 

I know this is an old thread, but thought I'd throw my two cents in.

About a year ago next month, I traded in my 2010 Dakota Big Horn 4x4 with 50k-60k miles in on a 2013 Ram 1500 Laramie Longhorn. Loved that truck. This 2013 had 3.55 gears (only offered for the Hemi and 8-speed for the 2013 model year, starting in 2014 they eliminated it as an option unless you picked 6-speed or EcoDiesel).

In December, on a clear day with no snow or ice on the ground, a semi blew a red light and took out my front end at 45 MPH. Twisted the frame so badly that it was declared a total loss by my insurance.

When I finally got the check, I had to venture about four hours away from home, but found me a 3.92 2014 Ram Longhorn.

Different in gas mileage between the two is small, but its there. The 3.55 gears got about 1 MPG less in town (if I am easy on the skinny pedal), and about 1 MPG better on the highway. I only had the 2013 for six fill ups before she was struck, so its not the best comparison, but its close.