Went from 20inch rims to 20inch rims. And I got them done at Inland off hwy 183 War Horse, they were cheaper than 4wheel parts and did a great job on the install! The whinning is a 2 on a scale to 10. Gotta love Austin Tx!!!

 

Man I get around 11 mpg in town and got no higher than 16 mpg on an all interstate trip using cruise at around 70mph with 3.92. I have 33 x 11.5's though on 17's. Anybody wanna calculate my "sweet spot" in an empty truck??? :-)

 

It will be down near 55. You will not want to go that slow, you will get run over, hell, that will get you shot in some parts of the country.

 

lol.... yeah but I'll have one of the biggest trucks on the road! They won't mess with me!

 

When I had 3:21 I got an average 26 MPG on the Highway, with 3:55 I get 19 MPG on the Highway. No tire change or wheel size change, it's your gears.

 

Cross, can you be more specific as to the name of the installer? Also, were the gears after market or OEM? The reason I ask is that I've experienced a lot of gear whine with aftermarket gear sets.

War Horse: FYI - had a not so good experience with 4wheelparts (Austin) installing aftermarket 4.10's in my '05 Dakota. (Same 9.25 axle as our Ram 1500's). It's currently in the shop at Boerne Dodge installing OEM 4.10's. Not going to be cheap but hopefully done right.

If they do a good job on the Dak then I might have them change out my Ram's 3.55 to 3.92.

In hilly terrain, there is absolutely no question in my mind that a 5% to 10% lower gear ratio (i.e. 3.92 to 4.10 and 3.55 to 3.92) increases gas mileage about 20%

Here is why: On the Dak 4.7L with 4.10's the tranny stays in OD all the way to the top of the hills without downshifting. Also, When towing, there are fewer downshifts. That being said, on flat terrain such as I-10 to Houston, the MPG drops about 7% with the 4.10's.

I'm going to experiment with the Ram by using 2" shorter diameter tires to see if the MDS and overdrive stays engaged more often. If it works, I'll swap the gears out to 3.92's.

p.s. If I decide to do the swap, I'll pull my 3.55's and trade them to anyone that is unhappy with their OEM 3.92's. Will pull mine first and send them to ya since I have the Dak as a second truck and can deal with the down time.