Identifying a Transfer Case Seal or Prop Shaft Plug Leak

Automatic transmission fluid may be seen under the center of the vehicle on some 2015-2023 Escalade, Colorado, Express, Silverado 1500, Silverado 2500/3500, Tahoe, Suburban, Canyon, Sierra 1500, Sierra 2500/3500 and Yukon models equipped with AWD/4WD (RPO F48). Some models with an 8-speed transmission are not affected.

If automatic transmission fluid is found under the middle of the vehicle, verify if the red fluid is coming from the transfer case/transmission rear output seal or the propeller shaft slip yoke welch plug.

First, check the rear output seal and boot area for a fluid leak. (Fig. 6) If the output seal is leaking, replace the seal.

 

Fig. 6

 

If the seal and boot area appears to be dry, check the welch plug area. (Fig. 7) If the plug is leaking, replace the propeller shaft front slip yoke.

 

Fig. 7

 

If both the seal/boot and the welch plug are wet with automatic transmission fluid, making it difficult to identify the source of the leak, dry the area with a soft rag and drive the vehicle a short distance to initiate the leak. Perform the inspections again to determine which component is leaking.

Refer to Bulletin #22-NA-225 for additional information.

– Thanks to Robert Cross