2005 Mercedes-Benz S500 needs driveline fluid

Dear Doctor: I own a 2005 Mercedes-Benz S500 with 4-Matic all-wheel drive and 99,000 miles. When turning the steering wheel all the way to either side in a parking lot I feel a binding vibration, as I speed up or straighten wheel the feeling goes away. Also, the transmission does not shift as firmly as it once did. The dealer said the transmission and transfer case would need to be overhauled at a cost of $6000. What other solutions are there? Barry

Dear Barry: I see this type of problem on AWD vehicles of many makes. One of the biggest problems is the lack of driveline fluid changes. Every one of the vehicles I have serviced for these complaints had the original fluids in them and the fluids were burnt. In order to change the transfer case fluid on the Mercedes 4-Matic, the heat shield and transmission support needs to be removed to drain the fluid. The transfer case only holds a quart of fluid. I recommend using 3 quarts — two to flush the unit and one to refill it. The front differential fluid needs to be flushed using a power steering flush machine with a long plastic tube pushing it to the bottom on the case. Next, use the new fluid to push out all the old fluid. The transmission fluid and rear end differential fluid also should be drained and filled. Make sure the shop uses only Mercedes factory fluids. I recommend the fluids be changed every 50,000 miles or 5 years. I realize my recommendation time interval does not agree with the factory recommendation. — Junior Damato, Motor Matters

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