I had a thought and need some opinions. I have a 2005 Silverado 2500HD with the 6.0L. With 33" tire on stock wheels I get around 11-12 miles per gallon. I have noticed over time that when I drive 55mph as apposed to 70 I get better fuel economy; more than likly due to the lower RMP's, I guess aero dynamics could also be a factor.
But here is my thought, what if I swaped out the 4.10's and put in 3.73's. I don't pull things all that often, I probably should have bought another 1/2 ton but I got a great deal on this pickup.

So do you think it would be worth the probably cost $600-$1000 to do the swap?
If I can get 15mpg I would save .08c per mile. I would have to drive it for 7500 to 12500 for it to pay for itself.
Anyone know if my mileage will increase to 15? What if I went back to stock tire size, or even down to 265's?

I have 3.73's and want to get 4.10's. If you decide to swap let me know if you are close to Texas and the D/FW area. With 265's and the 3.73's I was getting just under 19 mpg.

WaSS... the 33's are costing you 1-2 mpg. If you pull much you'll want to keep the 4.10's, if not then you can get by with the 3.73, but power will drop a bit.

The air resistance at 70 is roughly twice or better than at 55.

I have 3.73's and want to get 4.10's. If you decide to swap let me know if you are close to Texas and the D/FW area. With 265's and the 3.73's I was getting just under 19 mpg.


Not too close to Texas, I live in Oregon State.
19mpg would be great form a 6.0L. I might start looking into this more.

I do pull things from time to time, but it's usually a single axle trailer with a max cap. of 3500lbs which it never sees. I cant see swapping ratios hurting the pulling I do too much. I probably never pull anything over 5000 lbs; no large travel trailers or campers.

Where is a good place to shop for gears at? I have Richmond gears in my car. I checked summit and they don't show much of a selection for newer pickups.

also take into consideration of how much local driving you do. with 33s 3.73s will kill you in town stopping and going.

and good luck getting 19mpg, thats wishful thinking

I think about the only way you will see 19 out of a 6.0 is to push it around town. :D

also take into consideration of how much local driving you do. with 33s 3.73s will kill you in town stopping and going.

and good luck getting 19mpg, thats wishful thinking

Actually I stand corrected, I think I have 32's they are 285 75 16's, not that it really changes things :)

If I did this gear swap I am also considering dropping to 265 tires.

I think about the only way you will see 19 out of a 6.0 is to push it around town. :D

I agree, 19 is a dream.

But if I could get 15 that would be nice. The 6.0L seems to be a decient engine, however I just can't believe that there isnt much that you can do to it to increase its fuel economy (i.e. cold air intake/exhaust/chip).

Then again it's nice knowing that no matter what driving conditions I am in gets the same fuel economy, 11mpg. I never get that 8mpg shock after hauling.

I have 285's on mine right now with 3.73 6.0 I get 11-13 city-hwy at 55-65 mph....and I feel like i have no power what so ever.

I think about the only way you will see 19 out of a 6.0 is to push it around town. :D
My cousin claimed that with a small chip his 03 went from 13 to 19 at 70mph. I have a 98 with some stuff done to it and I got 20.8 the last time I checked it and that was in West Virginia on small roads. If you are willing to do some work and research anything is possible with a GM smallblock.

I am GETTING just under 19 mpg with my 265's. There is NO wishful thinking. That is hand calculated. I have the mods in my sig. Now that I have the H2 rims and tires my mileage is no where close but I also don't have the computer programed for the new tire size. My tune helped the most. Everyone should get one.

i know its a different motor but my 81 pickup has gotten an all time best of 19 on the highway. 33x12.5" tires, 5.0L gas, sm465 so no overdrive, and 3.08 axle gears so i was turning roughly 2300rpms at 70mph. pulling a honda crv on a uhaul car trailer from midland texas to san antonio (through hill country) i got 13mpg loaded and 16 empty. open air element and a single 2 1/2" exhaust.

19 is hard to believe. My truck in stock form at 65 mph would only get 14-15.

My truck is not stock :) While stock I would get about 14.

5 MPG increase? I need a tune

I have 3.73's and want to get 4.10's. If you decide to swap let me know if you are close to Texas and the D/FW area. With 265's and the 3.73's I was getting just under 19 mpg.

Downhill with a tailwind and an egg under the pedal? I rarely saw 15mpg on the hwy w/stock tires on my '04 6.0. That's why I go big block w/a gasser. The measly 2 mpg loss it well worth the extra power.

I also have a 6.0l and get around 10 to 12 at any given time pulling 30ft trailers or not. I run 285s with 373s i would love to have 410s but ain't going to spend the money had to truck 7 years ain't done by now probley won't!! they remind me of the old 6.2 diesels there is no get up and go about them.

Might have to get rid of mine.:(

Changing the gears is not going to net you 11mpg to 15 mpg. No way. You can buy a lot of gas for the money you will spend on gears. If you have to have them installed, then figure on much more.

If you want to get better fuel economy, slow down, acclerate slowely put the stock tires back on and maybe look at a tune. Leave the 4.10's in there.

I had an 05 1/2 tonner 5.3 and it got 15.5 pretty much all the time. The guys I work with that had the same truck had 3.42 gears and got 1/2 to 1 mpg better than I did, and they downshifted on every hill they hit, and I very seldom did.

I say keep the 4.10's and buy a tune.

Downhill with a tailwind and an egg under the pedal? I rarely saw 15mpg on the hwy w/stock tires on my '04 6.0. That's why I go big block w/a gasser. The measly 2 mpg loss it well worth the extra power.
It was actually back from Houston. I guess technically that would be uphill :) I don't know about the wind but I was VERY easy on the gas.

My 1500hd 6.0 only gets a combined of about 12.3 mpg, I can see about 15-20 highway but i do mostly city but if i could get a little better say 15 combined id be happy.