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  #1  
Old 04-30-2001, 10:40 PM
AV AV is offline
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Location: Toronto,Ontario
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Hello
could someone please explain the function of this part and how to identify and change it.I have a flaring problem and am told that this part is hanging which causes this condition on a 1988 300E.
Anyone can shed some light on this,i will appreciate it very much.
Also what may one expect for the part.
Thanks
AV
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  #2  
Old 05-01-2001, 06:56 PM
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Small round *black* plastic diaphram on the left side of the transmission. Part number 126-270-43-79. Has vacuum line from engine attached to it. Just in front of electrical switch (neutral/backlamp). Function is to control *QUALITY* of shift.
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  #3  
Old 05-02-2001, 07:45 AM
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AV,

I also have a '88 300E (123000 miles). It also has a "flaring" problem with the 2nd to 3rd gear switch. This doesn't occur every time, but usually when I apply the throttle a little harder. The RPM revs from 2K to about 3K during the gear change. But the other gear changes are quite smooth.

Does your car exhibit the same problems?
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  #4  
Old 05-02-2001, 09:09 AM
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Before you go to the expense and bother of changing it, try adjusting it. If nothing else it will give you practice as the new one will definitely need adjusting. I would suggest turning the tee handle one turn clockwise.

The modulator uses engine vacuum to sense load and is used to vary shift pressure to suit the load of the moment. It works by placing a vacuum on a diaphram opposed by a spring. The adjustment varies the spring pressure and thus changes the hydraulic pressure in the trans called modulator pressure. This pressure works on the main system pressure regulator as the largest influence.

The proper diagnosis and adjustment of modulators (and thus modulator pressure) would to use a pressure gauge. While driving the pressure would vary greatly with engine load and change smoothly (if not sticking). The proper adjustment is achieved (by the book adjustment that is) by removing the vacuum and holding the rpms to 2000. (It turns out that the pressure is constant just above idle - the 2000 is to be sure the pump has good volume). The measured pressure would then be set to the value from technical data.
We do these measurements every time we rebuild a trans, but seldom afterwards. Afterwards we usually adjust them to feel.

BTW the tee handle is under the rubber cap in the center of the device. It pops off with a small screw driver and the tee handle is locked in the depressions of a castelated rim.
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  #5  
Old 05-02-2001, 12:39 PM
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Location: Canada
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W123 modulator?

Steve, I have a '79 300D that also has a flaring problem. I tried to locate the modulator, but didn't have any luck. Do all automatic MB's come with one? If so does the 1979 W123 have a similar set as you described for AV ( the 1988 300E)?

I also have an intermittent not-going-into-gear from Park problem. This never occurs after the car has been running, but happens (sometimes) when it hasn't been driven for a while. To get it going, I rev then engine in Neutral or Park for a bit, then I can hear a quiet metalic whirring sound. Once this sound happens, it goes into gear. I don't think adjusting the modulator will cure this problem though, but I would like to find out what might be causing this problem.

Thanks

Gary
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  #6  
Old 05-02-2001, 01:46 PM
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The 79 Diesel does not have a vacuum modulator. It has a fixed modulator. I have never had one that adjusting made any difference.

To get shift strength on that trans you will need to make it shift later with the mechanical linkage. (shorten)

About the only thing that might help the slow engagement would be if the filter is restricted. A new one might help. Probably nothing else simple. You might try an additive designed to soften seals when you change the filter. We use a product by "Lubeguard".
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  #7  
Old 05-02-2001, 02:54 PM
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Thanks for the reply Steve

I kinda thought that my problem would be complex or expensive to repair. I should have said that I already changed the auto trans filter. Sooo, I will try the seal softener idea and then see if anything changes.

Gary
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  #8  
Old 05-02-2001, 03:03 PM
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SB,
I can't seem to find LubeGuard anywhere.
Is that an Over-the Counter drug??
Thanks
Arthur
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  #9  
Old 05-02-2001, 03:20 PM
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Sometimes the spelling is the difference. Try Lubegard or go to http://www.lubegard.com .

They also have a customer service line at 206-762-5343.
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  #10  
Old 05-02-2001, 05:44 PM
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Quote:
Originally posted by stevebfl
Sometimes the spelling is the difference. Try Lubegard or go to http://www.lubegard.com .

They also have a customer service line at 206-762-5343.
Ahh, yes. The speeling !!

Very good and thank you .
Arthur
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  #11  
Old 05-07-2001, 08:44 PM
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Location: Brandon, MS
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vacuum modulator

Could someone give me the job# for replacing the vacuum modulator on an 88 300E. I have the CD manual, but cannot locate the job. Please advise, Thanks.

Marks88
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  #12  
Old 05-09-2001, 09:44 PM
AV AV is offline
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Thanks Guys!!

Thanks to all who replied so kindly.It appears this may not be a do it yourself job at all since it needs all these adjustments.Steve what kind of time will a dealer charge for this job.I have already got the valve.
A job # would also help.
Thanks a lot.
AV
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A.Velji
88 300E/Debadged and Monotoned
Euro light conversion
Clear corners
Performance muffler..(love itttttt!!)
White Gauges by Chris Henkel
alpine CD am/fm,Fosgate amp,Nakamichi sub ported in cabin,Fosgates separates.
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  #13  
Old 05-09-2001, 10:31 PM
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I'm not sure what "job" you are talking about.

If you are talking about the pressure testing , adjustment and diagnosis of your modulator/vacuum system; I would guess 2 hours labor. Including changing the modulator if necessary.

BUT, no self-respecting professional will install customer supplied parts. The basic reasons are economic but in my case it has to do with warrantee. There are no repairs that I don't warrantee and I am not interested in negotiating that.
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  #14  
Old 05-10-2001, 08:32 AM
AV AV is offline
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New MB part

Steve thanks for the reply.Just so that you know the part is brand new purchased from MB as i thought i would be able to install myself.

AV
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A.Velji
88 300E/Debadged and Monotoned
Euro light conversion
Clear corners
Performance muffler..(love itttttt!!)
White Gauges by Chris Henkel
alpine CD am/fm,Fosgate amp,Nakamichi sub ported in cabin,Fosgates separates.
http://members.rogers.com/seriousimportgroup/1.jpg
http://members.rogers.com/seriousimportgroup/2.jpg
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  #15  
Old 05-10-2001, 09:38 AM
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I understand and we do make exceptions sometimes in such cases. But, the problem is not with whether you would bring a good part or not, to me. If you brought your own part I could not warrantee it and thus I could not warrantee the job and I don't do it any other way. I do not get involved with "I warrantee the labor" "you warrantee the part". This always leads to disagreements. I have no disagreements with my warrantee policy. I warrantee everything. No discussions.

I am pointing this out to the audience more than you personally. The economic reasons for not installing customer supplied parts are much to lengthy for this post.
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