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Old 10-20-2004, 10:59 PM
webwench
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Question Crazy question -- my 300D shifts too smoothly!

Back on Oct 10, we did a valve adjustment on the 300D (only had to loosen up three valves, and yeah, I think the special wrenches are worth it), and on the test drive afterwards, I was amazed at the difference in the way the engine ran -- idled smoother, ran smoother, seemed to produce a bit more power. However, I noticed that I could barely feel the transmission shift at all, and the 1-2 and 2-3 shifts happened more closely together, and at a lower RPM, than usual. Only in a Mercedes would smooth shifts be noteworthy Then the car sat for about a week while I waited for some new injector return lines...

Today the lines came in, so I put them in, and also adjusted the bowden cable (took up a little slack), and took a drive. (Also cleaned that banjo bolt thing, and opened up my virgin ALDA and gave it about 1/2 turn CCW -- nice!) The transmission is now shifting at what I think are good points, but it still shifts unusually smoothly.

Could smooth shifting indicate a problem? I'm so used to a fairly harsh shift at the 1-2 shift that this smooth shifting seems abnormal.

Also, is there a way to clean that vacuum line that goes from the switchover valve on the firewall to the intake manifold/banjo bolt, or is it just an item you replace? Mine looks to have crap in it.

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Old 10-20-2004, 11:24 PM
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Lucky you, I have my AT modulator out right now waiting for a new one to try and smooth out the shifts. I wouldn't worry as long as it always shifts without slipping and everything appears normal.


On the other subject, I disconnected the vaccume line at both ends and washed it out with carb cleaner. It helped to unscrew the switchover valve to get to the bottom line better (the one that gos to the manifold)
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Old 10-20-2004, 11:49 PM
carson356
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smooth shift

Hi, if you feel it is too smooth, you can adjust the shift quality. if you are familliar with the vacuum modulator on the transmittion, remove the little black cap pull out the little T shaped center part, turning it in will make the shifting more firm, and turning it out will make it more smooth, the only variant that may be is if the modulator has been updated to the new style, in which case the adjustments will be the same except you can only turn it with in a specific range, it loks different without the black rubber cap but a white plastic cap with a lever to turn it. i have removed the cap to re-position the adjuster to allow for more adjustment. what you are doing by moving this is increasing or decreasing the modulating pressure. please if you have any questions pleas let me know.
thanks Ray
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Old 10-21-2004, 12:58 AM
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The reason that it now shifts more smoothly is that you are pressing down less with your right foot. With the valves adjusted properly, the engine is putting out a bit more power and you are not pressing the pedal as far. This causes the vacuum to the transmission to climb slightly and results in smoother shifts. If you press down further and allow it to rev higher, the "smoother shifts" will return to the typical shift that you previously experienced. Every so often, with just the right pedal position, the 3-4 shift will follow the 2-3 too closely. I have never been able to figure out why.
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Old 10-21-2004, 02:48 AM
84W123DT
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Quote:
Originally Posted by webwench
... However, I noticed that I could barely feel the transmission shift at all, and the 1-2 and 2-3 shifts happened more closely together, and at a lower RPM, than usual. Only in a Mercedes would smooth shifts be noteworthy ...
For model year 1985 300DT, CD, TDT a vacuum assisted amplifier was put in to improve the shifting vis a vis less harsh. Nice.
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Old 10-21-2004, 12:14 PM
webwench
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Talking

Thanks all for the reassurance. And thanks, rg2098, for the cleaning tip!

Quote:
Originally Posted by rg2098
On the other subject, I disconnected the vaccume line at both ends and washed it out with carb cleaner. It helped to unscrew the switchover valve to get to the bottom line better (the one that gos to the manifold)
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  #7  
Old 10-21-2004, 12:25 PM
Waitn For The Bus All Day
 
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I know how to fix it--I'll swap ya

Cheers,

Bill
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Old 10-21-2004, 12:31 PM
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Quote:
Originally Posted by 84W123DT
For model year 1985 300DT, CD, TDT a vacuum assisted amplifier was put in to improve the shifting vis a vis less harsh. Nice.
Didn't see this post before my last one...

Yea, my '85 shifts much smoother than my '81. I was showing my "new" '85 to a local MB mechanic and he pointed to the vacuum amp and said "This is one reason for this particular model year being more desireable then previous model years".

I like my passenger side power mirror Previous years didn't have the power mirror--at least on the 300td's.

Cheers,

Bill
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Old 10-22-2004, 09:00 AM
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My 83 300D has a power passanger side mirror, I don't think that was an 85 only thing.
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Old 10-22-2004, 10:10 AM
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Quote:
Originally Posted by rg2098
My 83 300D has a power passanger side mirror, I don't think that was an 85 only thing.
oops- I didn't specify..

My car is an '85 300td.

I've had several wagons and none of the pre-'85's I've had had the power mirror.

Was this an option?

Cheers,

Bill

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