2001 silverado 1500 4x4 ext cab what was the factory gear ratio?

There's no single factory gear ratio for a 2001 Silverado 1500 4x4 extended cab. The ratio depended on several factors chosen by the buyer or what the dealership had in stock, including engine choice, transmission type, and optional towing package. Common ratios included 3.73, 4.10, and possibly others depending on specific options.

To find the gear ratio of *your* specific truck, you need to:

* Check the sticker inside the driver's side doorjamb: This often lists the axle ratio.

* Look at the RPO codes (Regular Production Option codes): These codes are usually found on a sticker in the glove compartment or under the hood. Specific codes will indicate the axle ratio.

* Examine the axle itself: The ratio is usually stamped on the differential cover (though sometimes this is difficult to read).

Without this information from your truck, it's impossible to say for certain what the factory gear ratio was.