* Engine size: Different engine options often came with different gear ratios.
* Transmission type: Automatic or manual transmissions, and even different versions of each, would have different optimal gear ratios.
* Axle type: Different rear axle types (e.g., 10-bolt, 12-bolt) could have different gear ratios available.
* Truck configuration: Whether it was a 1/2 ton, 3/4 ton, or 1-ton truck affected the gearing choices.
* Options: Some options, though less common, might have influenced the gearing.
To find the gear ratio for *your* specific 1990 Chevy truck, you need to check one of the following:
* The vehicle's data plate (usually located on the driver's side door jamb): This *might* list the axle ratio, but it's not guaranteed.
* The owner's manual: This should specify the gear ratio.
* The differential itself: The ratio is stamped on a tag on the differential housing. You'll need to look underneath the truck to find this. (This is the most reliable method)
Without knowing the specific details of your 1990 Chevy truck, it's impossible to give you a definitive answer.
