GM S-Series Pick-ups and SUV's 1994-1999 Repair Guide

Extension Housing Seal



See Figure 1

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Fig. Fig. 1: Installing the rear extension housing seal

  1. Raise and support the vehicle safely using jackstands. If the rear of the vehicle is supported significantly higher than the front of the truck, the transmission fluid may not have to be drained for this service.
  3. Remove the transmission fluid pan and drain the fluid from the vehicle. This step is recommended, but may not be necessary if the rear of the vehicle is held higher than the front. What is important is that the sealing surface in the extension housing may be cleaned of fluid and debris before installing the new seal. If fluid continues to run out of the housing once the old seal is removed, then the fluid should be drained to allow for proper seal installation.
  5. Matchmark and remove the driveshaft. Most vehicles covered in this guide should be equipped with a slip yoke and the front of the driveshaft. In order to remove the shaft, disconnect it from the rear axle, and then carefully withdraw the splined yoke from the rear of the transmission.
  7. Carefully distort the seal using a punch, then pry the seal from the rear of the transmission housing. Be careful not to damage the sealing surface of the housing.

To install:
  1. Clean and DRY the sealing surface in the rear of the transmission housing.
  3. Coat the outside of the new seal with a non-hardening sealing compound.
  5. Carefully drive the new seal into position using a proper seal installation tool. Be careful not to damage the housing or the transmission output shaft upon installation.
  7. Align and install the driveshaft assembly.
  9. Remove the jackstands and carefully lower the vehicle.
  11. Immediately check and, if necessary, add fresh transmission fluid.