* Consult a parts catalog: Use a parts catalog specific to your vehicle (like a GM parts catalog, online auto parts store catalog, or a repair manual) to find the correct seal based on your axle type (e.g., 10-bolt, 12-bolt). The catalog will list the seal by part number and dimensions. You can then take that information to an auto parts store.
* Check the seal itself (if accessible): If you can remove the old seal, it will usually have identifying numbers or markings stamped on it.
* Check with a parts store: Provide them with your vehicle's year, make, model, and engine size. They should be able to look up the correct axle seal.
Simply knowing it's a '96 GMC Z71 with a 5.7L isn't enough information to determine the rear axle seal number. The axle type itself will determine the correct seal.
