better milage out of 2500?

[oakman]

Hi

I need a 3/4 ton truck for payload capacity and medium duty towing. The 1999-2003 silverado 2500 trucks are great but the 6.0l really seems hard on fuel. I need the 3/4 ton frame so I can haul 2650lb payload for short 10 mile trips on average( once a week ). The towing duties would be 6800 lbs at the most. The 5.3 motor seems to have the power for what I need. In many web forums the 5.3 is compared to the old 5.7 vortec for power and the two are fairly comparable. The 5.7 pushed the old 3/4 ton down the road so I figure the 5.3 should as well. I know the 4l60e is on the weak side so I would build it up HD.My thought is I need the extended cab and I would give up the 4x4 and long box to save weight so a 5.3 could push it down the road. The 5.3 was just a thought to save fuel but some other ideas have come about from searching on several forums, such as:

6.0l with a 4l60e beefed up to reduce the rolling friction of the 4l80e ?

5.3 high output heads (310 hp all aluminum "B" motor) on the 6.0l engine ,raise compression ?

5.3 matched up to the 4l80e;most likely too much for the 5.3 too push ?

These are just ideas and I know its a truck so mileage is never going to be outstanding but I figure one of these ideas may work for me.

I would really like to get a 3/4 ton pushing 17mpg . I have heard the 5.3 will bolt right in but I don't know what all is required.I suspect ecm,exhaust manifolds etc.If you have any suggestions other than those above I welcome your opinions. Thanks in advance !!

PS : Platform for mods would be a 2001 silverado 2500 ext cab 2wd short box.

[nlawson5.3]

I know i had a 01 2500hd single cab long bed with a tune CAI exhaust and drivin in the country i got 10-13mpg normal driving but with a trailer it seemed like gallons per mile (no just kidden but really like 6-8) but i live in kentucky so lots of hills. Lots of my friends drive diesels, i know the price of diesel is crazy but their trucks are still cheeper to drive per mile than my 4wd 96 5.7 truck.

I think a 4l60 with 6.0 wont last and a 80's hurt mpg

PS what ever you do just remember do it right the first time because doin things twice is expensive and fu*kin blows

[Sport91]

Im up to about 14 mpg with my 01 2500hd ccsb 4x4 thanks to nelson's tuning. Thats with 35" tires and a lil bit heavier of a foot than average.

[2500Ak]

01 2500HD magnaflow dual-in dual-out, CIA, 0w20 oil, stock 4.10 gears

18.5 mpg on a 400 mile trip from college back to Anchorage Ak. A lot of it has to do with how you drive, I pulled about 85 when cruising hit the limiter when passing. The syn oil and dual exhaust helped a lot too.

Honestly, the mileage difference between the LQ4 and the LM7 does not justify a swap. Tuning also has a lot to do with it. The 5.3 has more horsepower than the old 5.7, but the old 350's were set up for low end torque.

The 5.3's curve is very different, a lot of the power is up top and you'll end up downshifting a lot imo.