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#1
07-14-2004, 11:38 AM
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W140 Transmssion - hard shift
I have noticed that the 1-2 and 2-3 shifts on my 92 400SE are somewhat harsh - not quite a "thunk", but harsher than I would expect from this car. 3-4 shifts are quite smooth. The transmission is a 722.366
It's interesting because the shift is much smoother until the car reaches operating temperature. I've noted that the "harshness" is much more noticeable under light load, and in fact on a fast acceleration, the shifts seem quite smooth and quick. The transmission guy said the pressure to the modulator is within spec. The transmission fluid level is correct and the fluid and filter are new. I've given the vacuum modulator a couple of turns counter clockwise in an attempt to smooth shifting. I know very little about automatic transmissions, and am also unlikely to ask the transmission guy to dig deaper - as they have not demonstrated much transmission knowledge. I've done a fair amount of searching the archives, but am frankly at somewhat of a loss. Any thoughts? Last edited by rsmcmahon; 07-14-2004 at 02:59 PM. 
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#2
07-14-2004, 06:04 PM
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could be leak in vacuum line to the modulator valve, or an obstruction in the line.
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#4
07-15-2004, 12:03 PM
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As pointed out the lack of vacuum to the modualtor will make all shifts at full load strength. A stuck modulator will act similarly.
If one were to actually measure modulator pressure the difference is striking between pressure at vacuum and at zero vaccum. The proper adjustment by a gauge is done with the vacuum disconnected at 2000 rpms (it's the same at idle if you got good trans pressures, the 2000 standard is to be sure the pump is fully working).
__________________
Steve Brotherton Continental Imports Gainesville FL Bosch Master, ASE Master, L1 33 years MB technician
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#5
07-15-2004, 04:24 PM
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Will this eventually wear out or damage the transmission or anything else? I've noticed this on my car as well.
I also notice when I come to a stop, that the trans stills seems to be engaged all the way until I come to a complete stop at which the time it releases and the engine rpms blips up a little. Does this have anything to do with the vacuum as well?
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