How do you change front differential axle seal on 2002 GMC 2500HD?

Confused. You said front differential but the tailgate is covered with oil?

Please clarify which differential.

Roy

Inner Axle Seal and/or Bearing Replacement - Front Drive Axle

Tools Required
J 22833 Housing Drive Gear Seal Installer (9.25 inch axle)
J 2619-01 Slide Hammer
J 29369-1 Bushing and Bearing Remover
J 29369-2 Bushing and Bearing Remover (2-3 inch)
J 36600 Output Shaft Seal Installer (8.25 inch axle)
J 36609 Axle Tube Bearing Installer

Removal Procedure

Raise the vehicle. Refer to Vehicle Lifting.
Drain the differential carrier assembly.
If replacing the right side seal and/or bearing, perform the following steps:

3.1. Remove the inner axis shaft and housing assembly from the differential carrier case assembly.
3.2. Remove the clutch fork assembly components and the inner axle shaft from the inner axle shaft housing.
3.3. Install the inner axle shaft housing into a vise.
Clamp only on the mounting flange of the inner axle shaft housing.
3.4. Install the J29369-1, 8.25 inch axle, or the J29369-2, 9.25 inch axle, behind the inner axle shaft seal or the inner axle shaft bearing as necessary.
3.5. Install the J2619-01 (2) to the J29369-1 or the J 29369-2 (1).
3.6. Remove the inner axle shaft seal and/or the inner axle shaft bearing using the J 2619-01.

If replacing the left side seal and/or bearing, perform the following steps:

4.1. Remove the differential carrier assembly.
4.2. Place the differential carrier assembly into a vise.
Clamp only on the mounting flange of the differential carrier assembly case.
4.3. Remove the inner axle shaft using a hammer and a brass drift.
4.4. Install the J29369-1, 8.25 inch axle, or the J29369-2, 9.25 inch axle, behind the inner axle shaft seal or the inner axle shaft bearing as necessary.
4.5. Install the J2619-01 to the J29369-1 or the J 29369-2.
4.6. Remove the inner axle shaft seal and/or the inner axle shaft bearing using the J 2619-01.

Installation Procedure
If installing the right side bearing, perform the following steps:

1.1. Install the inner axle shaft housing into a vise.
Clamp only on the mounting flange of the inner axle shaft housing.
1.2. Install the bearing with the square shoulder in using the J 36609 (1) and the J8092 (2)
If installing the right side inner axle shaft seal, perform the following steps:

2.1. Install the inner axle shaft housing into a vise. Clamp only on the mounting flange of the inner axle shaft housing.
2.2. Install the new axle shaft seal using the J 36600, 8.25 inch axle, or the J 22833, 9.25 inch axle.

Install the inner axle shaft into the inner axle shaft housing.

Carefully tap the inner axle shaft into place with a soft-faced mallet.

Install the clutch fork assembly components.
Install the inner axle shaft and housing assembly to the differential carrier case assembly.
If installing the left side bearing and/or seal, perform the following steps:

6.1. Install the bearing with the square shoulder in using the J36609 (1) and the J8092 (2)
6.2. Install the new axle shaft seal using the J 36600, 8.25 inch axle, or the J 22833, 9.25 inch axle.
6.3. Install the inner axle shaft into the differential case side gear using a soft-faced mallet until the retaining ring on the inner axle shaft is fully seated within the groove in the differential case side gear.
6.4. Pull back on the inner axle shaft to ensure that the inner axle shaft is properly retained in the differential case side gear.
6.5. Install the front differential carrier assembly.

Fill the differential carrier assembly. Use the proper fluid.
Lower the vehicle.

Good luck

Roy