Diagnosing, Adjusting and Fine Tuning Mercedes Automatic Transmissions

You CAN do this yourself if you have the right information and equipment!

High Mileage and age can raise havoc on the shifting patterns of an automatic transmission. Even if the fluid has been changed on a regular basis, they still wear out. Seals harden and leak both internally and externally. Vaccum and cable shift controls leak and fail. Rubber hose connections crack and work loose. And quite often some mechanic gets in there and messes things up. Tired of the clunking, slipping, or shifting too soon or too late? - then read on...

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Problem & Solution

Common among these chassis:


Many shift related problems can be solved without tearing down the transmission. Particularly on diesel automatics, an external control component or loss of vacuum could be the problem. Kent has developed a number of kits and manuals that will help you solve your transmission woes. As diesel automatics age the problems become more complex and the solutions more challenging.  Automatics in gas cars can also have problems but they are not as complex. When "de-bugging" an automatic transmission shift problem you need to go about it in a systematic manner. Just throwing money and parts at the problem will usually not work.

Before assuming the worst I recommend you do the following:

  • Don't spend any money on expensive parts until doing a proper diagnosis
  • The manuals and test kits I offer will help you isolate the problem
  • If you are having a shop work on your transmission be extra cautious
  • Get more than one opinion if seeking help from a transmission shop
  • Watch my on demand video on Intro to Troubleshooting Automatics - this will help you decide if you want to fix it yourself
  • Think outside the transmission first. Many problems are external. Follow the sequence below

Before considering a replacement transmission read my diesel transmission tuning manual. It will walk you through 8 phases of diagnostics and repair to get your transmission shifting properly. You may be surprised to learn just how many problems can be "adjusted out." 

This 125 page transmission tuning manual and associated repair kits will help you "fix it yourself" and possibly save hundreds of dollars.

During the time I have spent testing and tuning transmissions, I found a number of products that are easy to install and can help improve transmission performance. Sometimes a $3.00 part can go a long way to fixing a BIG problem.

Please click on any of the related products listed to learn more.