* Specific rear axle type: Both trucks used a variety of rear axle types (e.g., 14-bolt, Dana 80). You need to identify the *exact* axle type in both the donor (1998 1-ton) and recipient (2001 2500HD) vehicles. Just knowing it's a "1-ton" or "2500HD" isn't sufficient. Look for casting numbers on the differential housing.
* Axle ratio: The gear ratio (e.g., 3.73, 4.10) must be compatible or you'll have speedometer issues and potential drivetrain problems.
* Bolt pattern: The wheel bolt pattern must match.
* Spring perches: The location and type of spring perches need to align with the 2001 2500HD's frame. This is a critical area for fitment.
* Brakes: Brake systems might differ. You may need to adapt brake lines and potentially calipers and rotors.
* ABS: If either truck has anti-lock brakes, the ABS sensors and wiring harness compatibility must be considered.
In short, you need to get the specific details (axle type, ratio, etc.) of both rear ends before concluding if they're interchangeable. A parts store or a mechanic specializing in GM trucks will be able to help you determine compatibility based on the axle codes. Simply looking at the year and weight class isn't enough.
