On my wife's 90' 300E the trans shifts like a champ, but sometimes will not engage overdrive. Shifts and acts just fine other than that issue. Stop the car at a store or something where you shut it off and restart it, and it usually will start engaging OD again. Sometimes starts engaging OD after it has warmed up good...other times waits for a off/on cycle.

Fluid is full, appears to be clean and smells ok. All other shifting is ok, so I doubt it is a dirty filter or bad modulator. Is there a throttle position cable or a position sensor that might cause this type of behavior ? Vacuum line somewhere ?

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Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey