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  #1  
Old 04-20-2004, 08:41 AM
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What is the plastic thingy next to the ALDA?

The white plastic thingy next to the right of the alda with several vacuum lines going in and out... what does it do? Mine will only hold 10 vacuum and is an aparent vacuum leaker. What vacuum should it hold? Thanks

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Old 04-20-2004, 09:45 AM
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That thing is supposed to leak, well, sort of. It controls the strength of the vacuum to the modulator which controls shifting firmness based on throttle pos. There is quite a lot of info here on this vacuum valve. Have fun with it,
Adam Bush
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Old 04-21-2004, 02:12 AM
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It should hold about 15 pounds untill throttle is opened to a certain point then it dumps its vacuum activating the modulator on the transmission.They are spendy for a small plastic part......

William Rogers......
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Old 04-21-2004, 09:58 AM
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MrFarht,

If you remove the tri connector, make sure you put it back on correctly. One leg has a restriction, should be marked with a plastic clip, and that end must be connected to the vacuum supply.

I connected mine wrong and it ruined the transmission because full vacuum was on the transmission all the time.

P E H
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Old 04-21-2004, 03:05 PM
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OOOPS..

I removed all the connectors and don't see any difference in them. I have plugged the black vacuum line off. I think this is the one that goes to the transmission. It is shifting hard, but all gears are working. In fact, I kind of like the harder shifting... no flaring or slipping.

Does anyone have a picture of how the vacuum lines should look here? I have diagrams from the mercedes CD but I can't figure them out. I should have been more carefull and made some diagrams or photos. My main vacuum line has two connections in addition to the brake booster... 1982 300D turbo...

Many thanks to all who are helping.
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Old 04-21-2004, 03:38 PM
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There are some on my site. Unless the line to your tranny is leaking generally this is the root of the flaring problem. If yours only holds 10" rather than the 15-17" that it should you probably get a clunk going into and out of first as well. Seems like it prices in around $140, I should get one here fairly soon. Mine isn't horrible but it could use improvement!
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Old 04-21-2004, 10:04 PM
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Mr Good,

Are you sure one lead of the the tri-lead doesn't have a restriction in it? You can tell by blowing into each of the holes. One should have a noticeable restriction. That is what varies the vacuum to the transmission when the vacuum valve opens and closes. The lead with the restriction must be connected to the vacuum supply.

If there is no restriction, the transmission will get full vacuum all the time. When I connected the tri-lead wrong, my trans started slipping in about 2500 miles and I had to replace the trans.

P E H
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Old 04-21-2004, 11:12 PM
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Quote:
Originally posted by P.E.Haiges
Mr Good,

Are you sure one lead of the the tri-lead doesn't have a restriction in it? You can tell by blowing into each of the holes. One should have a noticeable restriction. That is what varies the vacuum to the transmission when the vacuum valve opens and closes. The lead with the restriction must be connected to the vacuum supply.

If there is no restriction, the transmission will get full vacuum all the time. When I connected the tri-lead wrong, my trans started slipping in about 2500 miles and I had to replace the trans.

P E H
Some models had a plastic orrifice of varying color/size. It's one of the ways to "tune" the shifts.
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Old 04-21-2004, 11:52 PM
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I presume you found 10"hg by hand pump, this implies a bad valve. Now if the valve were good and the vaccum wasn't strong enough then a larger orifice could be used.
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  #10  
Old 04-22-2004, 10:11 AM
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Thanks for the responses. Your DIY site is terrific Mr Boostbenz. I definitely am missing some proper fittings in my Vacuum system. I will study your great pics and report back.

Will it hurt the transmission in any way if I leave it plugged off and accept the harder shifting? I kind of like it... I have modified my driving and throttle style to accomodate the harder shifting but don't want to damage anything.

I am a gently driver and don't push it.
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  #11  
Old 04-22-2004, 10:20 AM
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Thanks.

I doubt it'd hurt the tranny but the rearend and flex discs may not enjoy if it slams into and out of gear, short term I wouldn't worry about it though. The valve should be able to adjust to a harder setting if you desire a harder shift without it slamming into gear.

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