I may have posted something about this previously but since I first noticed the problem in our '90 300TE well over a year ago, I will start a new thread with my updated findings.

Symptom is when auto tranny reaches normal operating temperature second gear is held longer than normal when accelerating up through the gears (at full throttle it will hold second beyond redline until the overspeed fuel cut-off is reached). When the change to third does occur it goes straight through to fourth gear (virtually skipping third). When cold all ratios are used as expected. All other transmission behaviour is normal with smooth changes hot or cold and no slipping or flaring. It will happily change back to third under load and will change up to third if "3" is selected. Normal starts use second and wide throttle starts use first as expected. This symptom has existed for well over a year (probably 15,000km) without getting obviously worse.

Last weekend I was doing the (major) 180,000km service which included transmission fluid and filter change. While draining the fluid I noticed it appeared darker than it should (dark plum colour rather than cherry or strawberry colour). It did not smell burnt though. After draining the pan and torque convertor, there was also the correct quantity of fluid, ruling out under or overfilling. With the fluid out in the sunlight it glistened with the appearance of what was obviously very fine metal particles. The pan and top of the filter also had some larger particles (up to size of large grains of sand) sitting there.

With new fluid and filter the transmission began behaving normally within a day of my service. Changes are smooth without slip or flare. They now occur when expected and all ratios are used. My question is what to do from here? With the now normal tranny behaviour I am tempted to just wait and see what happens. At the same time I don't want it to let us down suddenly at a bad time. The condition of the old fluid is a matter of concern. I am wondering if it may have missed the last fluid and filter change at 120,000km (we purchased the car at 124,000km over five years ago). The history showed (some) MB dealer service history and we purchased the car from a (different) MB dealer. My faith in their work was lost when on the first longish journey in the car (on the second day we owned it) the transmission spewed fluid over the underside of the car and up over the tailgate. This was due to the overfilled transmission overflowing when reaching a higher temperature on a long drive. This led me to believe the dealer may have changed the fluid (and filter?) but it may have been that they simply topped it up (too much). I had to drain about an additional half litre on that occasion to restore it to the correct level when hot.

If the fluid and filter change at 120,000km was missed, it may have gone as far as 120,000km without a change (our Oz spec versions recommend tranny fluid and filter every 60,000km). Could this result in the condition of the old fluid? Could the filter have become clogged and was bypassing fluid without filtering? Are fine metal particles normal wear and tear and to be expected after a possible 120,000km without a fluid or filter change? I would be interested to hear opinions of others, especially anyone with good knowledge of these auto transmissions.

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107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.