Transmission... Adjustment, maintenence, or impending doom? - Mercedes-Benz Forum
 
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#1 (permalink) Old 03-21-2008, 02:14 PM
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Transmission... Adjustment, maintenence, or impending doom?

The tranny in my 300CD is acting funky.

Under most normal circumstances, it drives and shifts perfectly, and always perfectly when the tranny is still cold.

Once it's warmed up, it does some other things. Under most normal, easy driving, it's fine. Under harder acceleration, it shifts fine until the last gear. The 3-4 shift is strange. It almost acts like it's two shifts. If you gently let up on the throttle, it drops right into gear perfectly fine.

The kickdowns work fairly normally too, although I dont kick it down by matting the pedal very often. But sometimes, if I do, it almost slips out of gear for a sec, revs up very quickly, and then falls into gear. The fluid is in excellent condition, it looks like it just came out of the bottle. This is because it used to leak a little at the cooler. The leak turned out to be just a loose fitting. I tightened it and topped it off, and it has not lost any fluid since. I never let it get too low even when it was leaking.

The shifts seem to be timed correctly, but I'm not 100% certain of that either. They seem like they might be a nudge late.

Any suggestions would be helpful.

Aaron
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#2 (permalink) Old 03-21-2008, 10:08 PM
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no ideas?
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#3 (permalink) Old 03-22-2008, 05:02 AM
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i was having the same problem check your atf levels

1982 240d Light Ivory-623.
190,000 miles (as of September 15, 2008)
188,000 miles (as of March 18, 2008)
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183,000 miles (as of October 29, 2007)
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#4 (permalink) Old 03-22-2008, 06:58 AM
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The fluid level is perfect, and the fluid looks like brand new.

Having searched revealed a link for a 'how to' adjust the vacuum modulator. I'm wondering if that would solve my problem, although it does not seem quite right.

The tranny is definately slipping a little bit.

Here is the link:

722.118 Transmission Adjustments

If you have a symptom of early shift, slip shift or stacked upshifts, turn the adjustment "T" in (clockwise) to increase the pressure. More pressure, later shift.

If you have a symptom of late shift or no upshift, turn the adjustment "T" out (counter clockwise) to lower the pressure. Less pressure, early and softer shifts.

I would say the tranny is slipping. However, I'd also say it shifts on the late side. Since you can't adjust the modulator both clockwise and counterclockwise at the same time, I'm pretty confused.

Aaron-
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#5 (permalink) Old 03-22-2008, 07:00 AM
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And could someone explain the difference between 'slipping' and 'flaring'... I wonder if maybe I have some terms mixed up. I'm excellent with everything except transmissions... I have a basic understanding of how they work, but very little knowledge of how this one works, or is supposed to work.
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#6 (permalink) Old 03-22-2008, 10:01 AM
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Mostly that modulator deals with the "softness" of the shifting or how fast it will shift after it decides to shift. The bowden cable tells the tranny when it is time to shift. Taking the slack out of the cable makes it shift later, adding slack to the cable and it will shift sooner. Adjust both to your liking but I would adjust the bowden cable first as it is the easiest to get to.
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#7 (permalink) Old 03-22-2008, 11:24 AM
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Ok, that makes some sense. I wonder if just adjusting the cable will fix things. It might.

Aaron
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#8 (permalink) Old 09-07-2008, 01:06 PM
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Quote:
Originally Posted by MB-Owner-in-ind View Post
Mostly that modulator deals with the "softness" of the shifting or how fast it will shift after it decides to shift. The bowden cable tells the tranny when it is time to shift. Taking the slack out of the cable makes it shift later, adding slack to the cable and it will shift sooner. Adjust both to your liking but I would adjust the bowden cable first as it is the easiest to get to.
Where is the bowden cable located? pictures please. I have had my tranny professionally adjusted by a shop that I really trust but want to readjust it myself. It originally shifted very hard as these cars do so I told them to make it a little less harsh and now it shifts very soon and most of the time I shift manually to make up for the loss of power. I don't feel like going back and being the jack@$$ that says "hey will you change that tranny vacuum back"

1985 300TDT "Yellow Submarine" - 164,000 mi
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#9 (permalink) Old 09-09-2008, 07:51 AM
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My 1985 300D transmission is also acting "differently". It changes OK but does have hard shifts.

My car has the blue transducer that that the line to the transmission passes through.

Questions:

- If I disconnect the line to the transmission and pull a vacuum with a mityvac, should that line hold a vacuum?

- Where on the transmission is the modulator located? Can it be accessed by a 69 year old without a hoist

- If modulator needs replacing, is this an easy job for a DIYer?

Thanks!
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