Troubleshooting a Mercedes Transmission

by Sabah Karimi

Strange noises coming from the transmission of your Mercedes, difficulty shifting to higher gears, or leaking fluids are all signs that the transmission is wearing down or failing. There are several checks and tests you can perform to make sure the car's transmission is in good shape, and you do not need any special tools or equipment to perform some basic diagnostic tests. Here are a few tips to help you in troubleshooting a Mercedes transmission.

Check your valve hoses. The valve hoses in the Mercedes engine are located in a small black box on top of the valve cover. Check the tops of the valve covers to make sure they are not worn out; if they are, you will need to replace them.

Look at the color of the transmission fluid. Transmission fluid needs to be flushed and changed frequently, and the fluid is a deep cherry red in color. If it has become black or turned a dark gray, there could be an internal oil leak that is affecting your transmission.

Look at your transmission oil pan. A mechanic may need to remove this for you; if there is metal at the bottom of your transmission oil pan, the transmission will have failed.

Check your vacuum modulator. This part is responsible for telling the transmission when to shift. If it is not adjusted properly, you may experience an "early shift" or "late shift." Shift slips can be adjusted by turning the modulator clockwise to increase the pressure and initiate a later shift, or counterclockwise to lower the pressure and initiate an earlier shift.

Change your throttle pressure. Another way to adjust how the transmission shifts is by increasing or decreasing the tension of your throttle pressure cable. Make the slide shorter to make the transmission shift later, or make it longer to make it shift earlier.

Listen to the engine while it idles. An unstable idle or "growling noise" could be a sign of a poor intake air temperature sensor, bad engine coolant temperature sensor or a dirty throttle body. Make sure all these components are working properly to prevent transmission damage.


  • check A buildup of contaminated oil in the transmission filter is one of the most common reasons for transmission failure.


  • close Don't modify your transmission or any other parts of your engine if it is still under warranty.

About the Author

Sabah Karimi is a professional Web and print copywriter. She specializes in several niches including travel, fashion, beauty, health, fitness, lifestyle and small business. Karimi has an educational background in business administration and marketing from the University of Wisconsin-Platteville.

More Articles