TSBs

Verifying Chevy ATF leak spot

June 10, 2025

This bulletin applies to 2015-2023 Chevy Express vehicles. You may find red fluid (ATF) leaking from the middle of the vehicle.

Mike Mavrigian

Related To:

Mitchell 1

This bulletin applies to 2015-2023 Chevy Express vehicles. You may find red fluid (ATF) leaking from the middle of the vehicle.

Verify that the ATF leak is either from the T-case/transmission rear output seal or from the prop shaft slip yoke welch plug.

1. Visually observe the output seal and boot area.

2. If the seal/boot area appears to be dry, inspect the Welch plug area. If the Welch plug is the source of the leak, replace the propeller shaft front slip yoke. If the output seal is the leak source, replace the outer seal.

3. If both the seal/boot and the Welch plug are wet with ATF, dry the areas with a soft rag and do a series of short drives to initiate the leak and service as needed.

About the Author

Mike Mavrigian | Motor Age Editor

Mike Mavrigian has written thousands of automotive technical magazine articles involving a variety of specialties, from engine building to wheel alignment, and has authored more than a dozen books that crisscross the automotive spectrum. Mike operates Birchwood Automotive, an Ohio shop that builds custom engines and performs vintage vehicle restorations. The shop also features a professional photo studio to document projects and to create images for articles and books.