I know this has probably been beat to death, and I've read multiple threads on multiple forums, but haven't gotten quite a clear answer. I have a 2008 4x4 5.3L lifted 6 inches, with 35 inch tires. Cai, longtube headers, and tune. Currently have the stock 3.73's and looking to regear to 4.11's or 4.56's. My question is which one would be better for my needs? I rarely tow, and my city/hwy driving is about 65/35, but I do have an all highway 700 mile round trip once or two times a month at 70-75 mph the whole way. I'm mainly concerned with highway mpg's with the 4.56's. I know 4.11's are a good compromise between power and mpg, but I don't want to spend the money and time going from 3.73 to 4.11's and be disappointed with performance gains, and be left wishing I would've went with 4.56's. If I can't find a clear answer, my last resort, is to install 4.56's in the rear only and run through a couple tanks of gas and test out the hwy mpg's and make my decision after that.

4.56 - 4.88. 4.10 isnt enough for a 4.8 behind 35" tires. you probably wouldnt even notice the difference between a 3.73 and 4.10

Any input or experience regarding 4.56 hwy mpg?

You can use any of the multitude of gear ratio calculators on-line to figure the gear ratio you will need to install in your axles to return your truck back to its original overall gearing with the taller tires you’ve installed, but it still won’t account for the great increase in rotational mass, so with the 35’s and especially with the lower torque output 5.3L you will definitely want the 4.56’s or at least I would. Even though like I said, it doesn’t take into account the added mass, please run the calculations based off your new tire height and possible gearing vs the original components to see what it will take to basically put you back to stock and at least you will have it in the back of your mind that you’re not making a big error or someone is misleading you, it only takes a few seconds.

if you're worried about MPG, take the 35" tire off for a stock tire. your MPG is going to suck no matter what.

I've used the calculators, comes out to 4.21 which would put me at 4.30's, but not too interested in them because of the odd tooth count. The calculators give you the closet estimate to getting back to stock rpm, but I'm also looking for an mpg estimate. I need input from guys that have been there, done that

I know I know, "if you're worried about mpg, you shouldn't be driving a lifted truck anyway". I'm not to worried about mpg besides the one or two times a month when I have the long highway trip. Right now I get around 14-15 on that trip. I'm asking if changing to 4.56 would still be close to that, or would it be something like 10-12?

4.56 dont look back

I'll also be getting a stall, somewhere between 2600 and 3000

Well I have 4.56’s in mine with 31.9” tall tires and can still manage about 19mpg on the highway if I keep 65mph or lower. Anything much more than that and it starts deteriorating fairly quickly. I had the gears from back when my truck was NA and if I had already had the supercharger 1st I don’t imagine I would have ever went over 4.11, but it is what it is and I’m comfortable enough with them that I wouldn’t spend the money to re-gear both axles for the small amount of difference.

I can say one thing, with a boosted 6.0L I never have to worry about it downshifting or even unlocking the converter to make it up an overpass or was that a mountain…..