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  #1  
Old 02-24-2004, 09:09 PM
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Join Date: Jan 2003
Location: Sydney, Australia
Posts: 627
Is our 300TE auto transmission OK? Expert opinions sought

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.
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  #2  
Old 02-24-2004, 09:51 PM
190ESport's Avatar
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Join Date: Feb 2004
Posts: 10
Hi,

the particles you found and your oil seem perfectly normal under normal wear conditions. What is weird is your transmission failed to shift to third, i had that problem just before my tranny blew up and it was due to a faulty pressure pump inside the transmission.
However if you have no flaring or slipping when changing to other gears the pressure in your transmission should be fine. There is a sensor that controls transmission behaviour when car is hot/cold
it is mounted somewhere on the engine but i dont know exactly where on your model.

For now dont touch anything to see if the problem comes back.
In these cars i prefer to really come up with the right diagnosis before doing a repair because changing this and that around and having no result is very costly.
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  #3  
Old 02-25-2004, 02:15 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Old transmission fluid doesn't have the same viscosity as fresh, so the control and operating pressures were off, and the flow was goofy from the old fluid -- probably too thin hot.

Some metallic "dust" is normal. Actual metal flakes isn't -- indicates excessive wear on frictions. The friction material has a glittery look to it about like semimetallic paint --becomes visible as "sparkles" as the fluid flows in the pan, more less vanishes as grey dust when the fluid isn't moving.

I'd say the new fluid fixed the problem -- worth a try in the 300D shortly, as it does the same thing (almost skips third under light throttle).

Peter
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1972 220D ?? miles
1988 300E 200,012
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1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #4  
Old 02-25-2004, 06:21 PM
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Join Date: Jan 2003
Location: Sydney, Australia
Posts: 627
Peter & 190ESport,

Thanks for those reassuring replies. I must admit that the greatly improved tranny behaviour (which my wife noticed immediately as well) was reassuring but it is nice to hear opinions of others. I had never noticed the suspended fine metal particles on previous occasions (with different cars). Possibly due to the suspected problems I studied old fluid more carefully than I have done before. I am also suspicious that the previous fluid and filter change may have been missed. In future I will change it at the first sign of problems rather than waiting until the odometer suggests it is due. Peter, the larger particles sitting at the bottom of the fluid were very few in number and don't especially alarm me. I have been told of instances where trannies suffering problems like slow engagement and flaring changes (which ours wasn't) have large amounts of material sitting on top of the filter and in the bottom of the pan. It really was the fine suspended particles I was more curious about. Your 300D sounds like it may be suffering the exact same issue as ours was. It will be interesting to hear if a fluid and filter change has the same effect it did with ours.

Thanks,
Greg
__________________
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.
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