Non buick-related question on my Silverado

[Brer Rabbit]

OK I have an 05 3500 4x4 (not a dually) with that gas guzzling 8100 and Allison trans and 4.56 gears. Love the towing power but not the fuel economy as that dash computer shows an average of 8.6 mpg running around the city. On the expressway, driving really easy I have to fight to get10-12 mpg. I was wondering if a drastic change in the gear ratios would help this truck to get 16-17 mpg on the expressway. A friend told me he yanked the 4.10s and put 3.73 gears in his 2006 6.0 truck and he saw an incredible difference of like 5 mpg. He went so far as to suggest I go with 3.42s and believes it will not hurt performance. Has anyone tried this type of mod to a stock truck with a similar drivetrain? I know I will have to have the dealer recalibrate the speedometer but I would like to hear some thoughts on this please.

 

[Little6pack]

If the dealer cant recalibrate I think a hypertech would.

I have not done this on your exact truck but I had a 73 Z-28 that when I took out the 433 gear & put in 373. It made a world of difference on my CLUTCH foot, Gas milage & drivability.

As for the ET times who cares if you drop 1/2 a second for a street vehicle

 

[Brer Rabbit]

As for the ET times who cares if you drop 1/2 a second for a street vehicle

yeah I'm with U on that, its not about how fast it would be. Its only about being more practical in daily use.

 

[Quick6'n'-K.C.]

I really think if you put a box on the truck and stepped the gearing down,it really might make a few dents in the mpg for the better, and get alot more torque out of it.

Lets face it, its a gas gussler.

Keep the stock tire range and step down the gears. Is that allison a 5 speed auto?

My cummins is amazing, has the 3.55 gears and i really wished it had 3.08 gears with all the torque and how the truck is set up now with mods.
Its like 2nd gear take off, 3rd quick shift to 4th and 5th at 45mph at idle.

If you can install some thumb tacks outward on the gas peddle and not wear any shoes or socks, i bet you get better gas mileage

BW

 

[Little6pack]

If you can install some thumb tacks outward on the gas peddle and not wear any shoes or socks, i bet you get better gas mileage

BW

:biggrin: So true