My 2wd Sport has 3.55s and it doesn't hunt or downshift on the highway. It will pull all but the steepest hills in 5th at 70 all day long and still get 20-21 mpg. I agree the 3.92 are better for towing and in town acceleration but the 3.55s are fine for those of us that don't tow often or try to drag race the rice burners at every light.

 

The other problem with the 3.55 is that it is not limited slip. I have the 3.55 also, but run 5th without O/D often because the engine likes a bit more revs. I was on some ice two weeks ago that was only on one side of the lane and the T/C came on immediately and stayed on for the 60 seconds that I was on the ice. If I had L/S, the T/C would not have come on. In most applications, the T/C keeps me happy with the 3.55. Without T/C, I would have already changed the diff. gears to 3.92 or 4.10 for the L/S features.

 

I don't know where you guys are driving but here in the hills of WV the best I've ever seen was 15 mpg. Average mixed driving I see about 12. That's mainly city, very little highway. By the way I have 31" x 17" tires and the 3.92 gears.

 

Lots of discussion about 3.92 vs 3.21 or 3.55 here...I'm getting ready to order a new truck and I'm trying to decide between the 3.73 limited slip or the 4.10 limited slip. I'm ordering a 5.7 Mega Cab short bed. I will occasionally be towing a boat and carrying a cabover camper...but will be driving the truck more often empty or just with the boat (4500 lb). I know that the 4.10s will be better for towing, but since I won't always have a load I want to get reasonable mpg when empty. Does anyone think the rig will do poorly with the 3.73 when towing the full load? And how much difference do you think there will be between the 3.73 and 4.10 in mpg when driving empty on hwy at 75 mph?

 

The newer transmissions have fairly low internal ratios because the last two gears are O/D, so a lower rear end gear is not much of a sacrifice. If you are getting the 17 inch tires, 3.73 will be fine, if 20's consider the 4.10. With a boat that size, your truck will run better and cooler with less strain with the lower gear. Like all things in life, it is a compromise, but shoot towards the lower gear to be happiest with your truck.

 

Appreciate the advice man...I am oging to stay with the 17" tires. Because of the load I'll have, and the fact that I'll be running E rated tires, I would think 20s wouldn't be practical. Sound reasonable?

 

I think the 17 inch tires will be best for you. The LT rated tires ride much rougher than P rated tires. You should be able to find a 3.92 truck and split the difference, LOL. Look at the tow ratings for the different ratios and published RPMs. Did you say you are getting a 2500, are you getting a Hemi or Cummins?

 

My 2 cents on the LT tires: Standard on my '09 TRX are LT275/70/17 Wrangler AT/S vs. the HP which some owners have/had.

I am surprised at how well they ride and I am REAL PICKY about ride and road noise. The pleasant ride could be due to the suspension and frame isolators etc. though.

Only complaint is: A little bit of a whine but I suspect that is the tread lug pattern.

 

took a 500+ mile trip this past weekend.

I have 2009 reg cab long bed 4x4 hemi 17 inch wheels- 3.92 gears, completely stock

filled up with premium - I drove VERY light and keep the cruise on at 65 mph... sometimes 55 if that was the speed limit.

Math (which is right- no debate) tells me I got 20.8 miles per gallon

 

If anybody curious what the best mileage this truck can see...

With my '09 Laramie 4x2 w/ 3.92 gears and 20" tires.
I've got around 12K miles on it. I always put 89 octane in.

I've seen the following mileage:
In So Cal driving from Simi to the Valley (over a 1000 ft hill) I got 24 mpg (doing about 60-65)!! Just wife and kids in truck

From San Bernardino to LAX, around 20-22 mpg (doing 70-75+) just one passenger

I typcially see around 18 or 19 mpg (doing 65-70+) going from Simi to Palmdale and back. This is over a 3200ft. elev. grade w/ wife a kids.

Towing 6000lbs. with family around 8-9mpg.

to and from work and around town with lots of stops...about 15 mpg.

Just my 2 cents...