* Check the sticker on the driver's side doorjamb: This sticker often lists the axle ratio (e.g., 3.42, 3.73, 4.10). This is the *final drive* ratio.
* Check the owner's manual: The owner's manual *might* list the gear ratios for the specific transmission your Tahoe has (automatic or manual, and the specific model number).
* Look at the vehicle's identification number (VIN): A dealer or parts specialist can use the VIN to access the vehicle's build sheet and determine the exact transmission and axle ratios.
* Inspect the axle itself (requires some mechanical knowledge): The axle ratio is usually stamped on the differential housing.
Without this information, it's impossible to provide the correct gear ratios.