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I am thinking of changing my gear ratio from a 3.73 to 4.10 on my 02 Avalanche 2500 (8.1L gasser but similar HP and torque as a diesel). The towing capacity is 10400# with 3.73 and 12000# with 4.10. Both options were available from Chevy. It pulls OK from GA to FL (all flat), but I don't like the feel in the hills of the Smokies north of here.
Anyone ever done this? I expect to gain a little efficiency when towing (lose some when not). Any pros and cons or advice you can give?

Attached are my weights from my last trip if that is helpful. Curb weight of the truck is 6353#
 

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Well, first of all you do not have similar torque and HP to a diesel unless you compare to the early 2000's. Secondly a lower gear ratio will help help towing on the hills but you will go down in fuel mileage most other times. That being said, the lower gears will probably make every day driving more enjoyable but at a cost that will be a direct right off.....and since we only live once, do it if that is what you want to do. I did it in a Ford with a 460 back in the 90's....and liked it.
 

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Good info, Sledman. Changing to the 4.10 easiest way to get that much increased towing performance.
 

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Changing gearing is truly a double edge sword. GM really knows their stuff when only offering 3.73 with the duramax. With a gasser, 4.10 will help in some situations but not all. With each gear ratio there will be an optimum speed that the engine and gearing will pull the best. For example: On a hard pull towing a heavy trailer the sweet spot could be 2800-3600 rpms on a gasser, but the speed of your travel could actually go down with the lower gears even though the load on the engine would also go down because the change in gears isn't enough to allow the engine to pull a taller gear in the transmission. So, a person needs to identify what they are hoping to gain by performing a gearing swap.

In my younger days I played a lot with gearing changes, tires size changes and engine mods. One thing I learned is increasing power in the engine and leaving the gearing alone usually yields better results.

To the OP, consider a supercharger kit for the 8.1 and leave the gearing alone. If you had a duramax, increasing the power level results in being able to holding a gear longer helping increase speed pulling hills.

In the Fast Lane Truck testing of 2017 with Ford, Dodge and Chevrolet diesels running the Ike Gauntlet, Chevrolet won, possibly because of gearing, Chevy was the only truck with 3.73, the Ford and Dodge both had 4.10's. I would love to tell you that the Duramax is that much better of an engine, but in all honesty all of the new diesels are pretty evenly matched.
 

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Your gasser develops maximum torque at 4500 rpm, whereas the Duramax maximum torque happens in the teens. So based on that, switching to 4.10s may be advantageous. But don't throw away those 3.73s, in case you change your mind.
 

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The Silverado 2500 HD is available with any one of three engines, a 6.6-liter Duramax diesel, an 8.1-liter gas-powered Vortec V8 and a 6.0-liter Vortec base-level V8. ... Replacing the 7.4-liter V8, the 8.1 makes 340 horsepower at 4,200 rpm and 455 foot-pounds of torque at 3,200 rpm.May 9, 2001

Just sayin
 

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The Silverado 2500 HD is available with any one of three engines, a 6.6-liter Duramax diesel, an 8.1-liter gas-powered Vortec V8 and a 6.0-liter Vortec base-level V8. ... Replacing the 7.4-liter V8, the 8.1 makes 340 horsepower at 4,200 rpm and 455 foot-pounds of torque at 3,200 rpm.May 9, 2001

Just sayin
I stand corrected. That's what I get for going by memory.
 
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OP hasn't been back since the opening post.
 
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