The other thing to consider is that the 10 bolt axles have pretty small gears... you go any steeper than a 4.56 and you really start to deal with pretty small teeth... I think you lose strength there.

I would never go any more aggressive than a 4.56 in a half ton axle. 50 MPH at 6500 RPM doesnt sound bad to me at all. Thats pretty similar to a 60e with 4.10's in a stock 4x4 I think.

 

Dialed in tune, 93 oct, very very easy on the pedal.. isky 215/215 .566/.566 114lsa is just about perfect for DD, makes alot of Low end TQ.

975 miles round trip from my house to dallas, tx. averaged right at 24.
Did the speed limit the whole way. Its done 24 on several trips out of town. but i only average 17 on my dialy commute, 19 if i leave the house in time, and 13 this weekend towing some broke down vechicles.

 

The best I can squeeze out of mine is 17 on long trips, 14 around town. Need to get it tuned.

 

Very much so..
Get a wideband.
my AFR is 15.5 cruising and running around 40-42* timing at 2000rpms on 93, i had to back it down to about 38ish on 87 or id get a lil knock in there sometimes.

After you learn how to tune speed density, you can be very aware of fast throttle transistions.

 

Are you running OLSD? I'm currently running CLMAF but wondering if I should switch.

 

Yea OLSD, no MAF, its just used for a coupling for my stock airbox

 

You like OLSD better on a basically stock truck better than CLMAF?

 

Exactly! you want to keep the engine in its power band. That is what matters. You can very much increase mpg at higher rpm. I run 4.88 gears in my truck, specs in sig. and IMO its not too bad for what I use my truck for, and thats just fun, work, trips, towing. Ill drive it anywhere. A dyno should show where the sweet spot is.

Wow, 2000 @ 70. 3.73s? I have 4.88s and run about 2900 rpms @ 70, but it does'nt take many rpms to jump 15-25 more mph. A dyno tune will be very benifical here, where you can load the engine at a certain constant speed/load and tune the detailed AFR populated cells. That will make a purring of a engine.

Thats good mileage, and thats a good cam choice. Im planing a straight patten cam as well for my combo, for the added tq output. 228/228 112

 

If I stay around 1900rpm/71MPH, I can swing 20-24 all day long. Above 2k and that mileage drops to 15-17.

 

Like what has already been said it is important to stay in the engines power band but at the same time not. For example when I am cruising down the road here I can be going 55 and just under 1500 rpm, when i drop it into 3rd it shoots up to almost 2000. With that said when I am in 3rd, even know I am at a much much higher power I get at least 5MPG difference.

I have done a few tests and LOWER RPM is way better if your engine makes enough torque and horsepower to drive it down the road. I did a few tests on mine and it was pure electronic so I think its fairly accurate but don't hold me to it. My truck only uses 30-40HP to drive down the road depending on conditions. So it uses almost nothing to drive down the road. Anyway back on track lower RPM will be better if and only if the engine in question can put out the required power. If you think about it you may be in the engines power band at 2000RPM but compared to 1500RPM that is 500 rotations more a min!! That is a lot of extra gas being burnt. Anyway I would go for the 4.56 gears. Even then IMO that is way crazy.

Oh about the less power at a lower RPM that is true. I have noticed it very much so when I am driving. For the most part I can be around 35ish MPG and then a hill or something comes and it is just lost when you press the gas. I can go from 35 down to 20 just speeding up just barely. I personally want to build my 4.8 for torque and hp around the 1500 rpm mark. I wanna see what kinda MPG these engines and trucks can do. Anyway I hoped i helped in some way.