5.7 Vortec Gas Mileage Question

Cool Zr2 · January 28, 2008

This may be a stupid question, but....

I love my 99 Tahoe and hate the idea of parting with it, its been such a good machine, but the gas mileage is getting a bit old. And that I just flat out like the old skool style.

Now, anyone out there have 3.42 gears or 3.08's in their 4x4 5.7 vortec? I had a 96 ext-sb with 3.42 and if I remember it got like 18 mpg, my tahoe gets 15.5 with 3.73. I'm not afraid of gearing down cuz it never tows anything and its always on the highway.

zeppeloid · January 29, 2008

I have a 97 5.7 Vortec ext cab 2WD with 3.42 gears and get 18-21 mpg. Always above 20mpg on highway. I am always easy on the accelerator though. I think the 4WD may be costing you about 3-4 mpg.

s-ten · January 29, 2008

I have a 97 5.7 Vortec ext cab 2WD with 3.42 gears and get 18-21 mpg. Always above 20mpg on highway. I am always easy on the accelerator though. I think the 4WD may be costing you about 3-4 mpg.

I agree that the 4WD is costing you. The gears that you have now with 265 tires (standard Tahoe size) is about equal to the 235 tires with 3.42 gears in a 2WD. Plus the weight of the Tahoe over a truck.

But if all you do is highway driving then a 3.42 gear may benefit you but probably not enough to overcome the cost of changing both differentials.