double overdrive

[66redw/white]

i was brainstorming the other day tryin to figure out how i could get alittle better gas mileage from my ol tahoe. 01 4wd, 5.3, 3.73, and 33" tires. right now it has a programmer, borla straight through muffler, and a k&n intake. im getting about 15 mpg. well 13 to 15 when i drive it and 15 to 16 when my wife drives it. one of my ideas was to change the gears to 5.13 and pick up one of those gear vendors over underdrive units. that would give me a .50 over drive for the highway and those steep gears should help out around town. any body ever see anything like this done before? i think i should be able to get at least 5 extra mpg outta the thing at a minimum.

[swb85]

Originally Posted by 66redw/white

i think i should be able to get at least 5 extra mpg outta the thing at a minimum.

Extremely doubtful. The problem isn't the rpms at all (70mph is only 1700rpm), it's the fact that you're driving around in a 5000 pound tank with big heavy tires and the aerodynamics of an apartment complex. I have the exact same vehicle as you, and even with longtube headers/dual exhaust and a custom tune we usually average around 16 in it.

[usmcchevy]

I think you could get 20 hwy out of her, but not that way. I forgot how much a GV unit is these days ~3k? Along with another ~1k for gears front and rear. You can buy A LOT of gas with $4,000.

1, Go back to stock tires, or maybe a little taller, but no wider than stock. The 33s are going to be a loosing battle.
2, E fans from a 98-02 Camaro ~$100 for the fans $100 for the harness.
3, Ditch the programmer and get a real tune. A dyno would be the best, but mail order will do. ~$200 at www.blackbearperformance.com

Keep it under 70mph and you may hit 20mpg Highway.

[66redw/white]

i was thinkin as far as city mileage goes that those gears would help lug that heavy truck around. although your definately right 4000 bucks can buy a TON of gas. lol.
the problem with this truck is its 4wd. id like to lower it and get some shorter tires for it but every time i look into it i end up askin myself if im really goin to lower a 4wd.
i have been lookin into the e fan thing. camaro fans will work? if i can get this truck close to my sierra in gas mileage (18mpg city) ill be happy. i just paid the thing off and my wife is acting like she wants somethin else because of the gas.

[usmcchevy]

Yep 98-02 LS1 F-body fans or even the older F-bodys with the LT1 work. Set them in there, add a few zip ties and then wire them up.





You will need a computer tune with pin 42 enabled in order for this to work.

[66redw/white]

so im pretty dumb when it comes to electrical stuff but how does the 1st relay get its signal to close? should be some kinda temperature sensor right? wheres that go at?

[usmcchevy]

From your trucks computer. Your computer will need to be tuned in order for it to work though. If you go to www.blackbearperformance.com they sell the E-fan harness pre made and can also tune your computer.

[66redw/white]

awesome. thanks man. youve been a big help

[66redw/white]

i fixed my problem with the gas mileage! traded my tahoe for my old blazer back! went from 13 mpg city 16 highway to 18 city 22 highway for free!..... ish. either way you guys were a great help