Bad Transmission–What Does Inspecting the Fluid Tell You?

This Chevrolet Trailblazer has a badly worn transmission that needs replacing. Driveability issues and noticeable symptoms like slipping & starting in the wrong gear with no power led us to the next step of dropping the oil pan to inspect the transmission fluid. (A vast majority of transmissions have a closed system–you can’t just drain and replace the fluid as with the engine oil. For this vehicle, you must spend about an hour actually removing & replacing the bottom oil pan in order to “inspect” the fluid. Viewing the fluid in a transmission is key to assessing the health & longevity of that system.)

According to the customer, this 170,000 mile plus transmission had only been flushed/serviced TWICE prior to our inspection. New transmission fluid is a clear reddish color. However, as you can see in the video, this fluid contains a catastrophic amount of muddy residue (clutch friction material) and metallic particulate (internal steel plate shavings) that show how the inside of the transmission is deteriorating, likely due to both high mileage and infrequent services. As designed, the circular magnet on the left has attracted metal in addition to the sediment in the bottom of the pan. The internal clutches are breaking down and mixing with the fluid designed to keep everything well lubricated and smooth. That’s what the goop and black specks are–tiny pieces of the transmission that are breaking away!! (Note: this pan is completely silver and shiny when empty.)

Diagnosis: total transmission failure is imminent. Unit must be replaced.

We always recommend transmission flushes and services about every 50,000 miles, regardless of what your owner’s manual states. (Being proactive in this case is best in our experience.) A full synthetic flush, preferred, is about $150. Other transmission services include filter replacement, pan cleaning, or band adjustment depending on the make and model. If you wait to service a transmission until you notice a problem, it is often too late to stop internal damage. Despite flushes, transmissions do fail eventually due to mileage and heavy or improper usage; however, lack of service will expedite this failure and cost you time off the life of the transmission.

Video provided by Forest Automotive: Complete Auto Service and Repair for Lynchburg, Forest, Goode, and Bedford.

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