Information regarding browntop/bluetop solenoids and TCU control tables.

Information regarding browntop/bluetop solenoids and TCU control tables.

Been many issues with transmission swaps and shift issues that come down to pressure control solenoid types and TCU calibration tables for brown-tops and blue-top solenoids.

Example: A person has a 2006 CLS55/E55/SL55/CL55/S55 car that came stock with blue top solenoids and they swap in a used wreaking yard transmission that has brown tops unknowingly? Symptoms are:

  • Slow and smooshy into gear and reverse engagement or no engagement feel at all.
  • Wonky and slip feel part and med throttle shifts.
  • Car shifts like a turd.

This is due to TCU being calibrated for blue top solenoids and not backward compatible for browntops.


You can use a TCU that is calibrated for browntops and swap in blue tops and works just fine but cannot be other way around.

  • TCU is calibrated for browntops you can swap in blue top solenoids and works well.
  • TCU is calibrated for Bluetops and used with browntops = Could cause internal clutch wear and burn spots on steels and will shift like crap.

How do I know what solenoids I have?

  • You can drop the valve body and visually see the color of solenoid caps, either will be blue or brown/black
  • Use a scan tool and get SCN 4-digit code number for tcu or part number of tcu and email me and I can look up what calibration is used.
  • Bluetops were used in many different Mercedes chassis, not just only m113k cars. I have a way to look up by vin #
  • Just because trans says 722.643 does not mean it has blue tops stock!

Replacing a transmission is always best to drop the valve body and check what color of solenoids you have and check out the replacement transmission if it matches, mise well do the conductor plate at the same time.

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