2007 Silverado Changing Diff Gears from 3.73 to 3.42

[Vortec-Z71]

Like everybody else said, not worth the time or money. Gains, if any, will be minimal. It would take quite a few miles just to break even after the swap. If you want MPGs, get a tune. 3.73s with the 4L60E are a pretty good combo.

[Mikeb52r]

With the 20" rims, keep the current gears. Depending on the truck's mileage, make sure you have a good tuneup (wires, plugs, O2 sensor). You will be fine otherwise.

[rdnkcpa]

Driving habits and a good set of tires will be more cost effective than swapping out rear-ends. When I switched from the factory Goodyears to the Bridgestone Revo's, I took an immediate 1MPG hit.

 

I would shop for a good set of all seasons, more street tire than off road, if that makes sense. The lighter the tire and rims and lower roll resistance, the better MPG.

 

As stated above, keep the MAF sensor clean, and change out the upstream O2 sensors and that will help as well.

[TRCM]

The cost to make the change in both axles will run you between $1000 to &1500, and triple that if you have the dealer do it.

 

I am not going to do it here, but I ran the math for a friend of mine who wanted to go from 3.73 to 3.42 last month. It would have taken him, at todays gas prices, over 100,000 miles to recoup the costs in saved gas.

 

if you really want to do this, find someone who wants to go the other way, and just swap complete axle assemblies.