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  #1  
Old 09-14-2010, 12:19 AM
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W126 560 SEL trans shifts harsh

So I went under. There is a new vacuum line installed. But the dial thing it attaches too looks like it *might* be factory. It looks like it turns to be adjusted? So I did. No change.

So what could be defective. I thought I recall reading about the trans shifts being vacuum dependent and a part failing. Pics?

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Old 09-14-2010, 09:11 AM
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With the engine running, do you have vacuum at the modulator on the drivers side of the trans?
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Old 09-14-2010, 11:25 AM
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I will check. But its a straight line to the intake, so I would think so. The line is new and connections intact. Although odd that the line is new.
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Old 09-14-2010, 08:05 PM
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Simply having vacuum present at the input to the modulator is no guarantee that it is working. If you have a MityVac or similar attach it directly to the shift modulator and see if it holds a vacuum. If not, that is your problem and it needs to be replaced.

The part is inexpensive (about $35 as I recall) but was difficult to access on my 560SL without a lift. You may have more room on your car.
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Old 09-14-2010, 11:05 PM
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If its the part the vacuum line goes right too, it seems easy to replace. Guess I will find out.
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  #6  
Old 09-15-2010, 06:49 AM
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shift modulator

Yes, that's it. There will be almost no fluid loss when you remove it.
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Old 09-15-2010, 01:06 PM
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After you install

the new one, there may be a short period of trial and adjustment until you have the shift characteristics where you like them. Drive, adjust the modulator if necessary, drive, adjust, etc.
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Old 09-15-2010, 10:09 PM
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Am I correct that adjusting it is as simple as moving that lever? If so and I am getting no change, I am betting its shot then. I will just replace it. I get parts at dealer cost, so no big deal.
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Old 09-16-2010, 12:26 PM
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Any leak in a vacuum pipe end, or in a A/C pod will also result in harsh shifting as will a old & leaky modulator valve .

mak
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Old 09-17-2010, 06:56 PM
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Where can I get a modulator. My usual parts guy where I get goodies at cost can not come up with one, even through his import channel.
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  #11  
Old 09-21-2010, 01:17 PM
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Right here

on this site. Get Phil before he retires.

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