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#1
12-19-2002, 01:48 PM
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300SDL AT vacuum amplifier
What does the AT vacuum amplifier do? I disconnected mine as an experiment, that is I connected the line to the transmission directly to the damper on the vacuum unit on the side of the IP. My initial feel is that it shifts more predictably. Maybe a tad softer.
BTW, there's a line that runs from the VAC port of the amplifier to the area of the fusebox. I lose track of it in the harness. It's not in any of the 124/126 vacuum line diagrams in the CD manual but the 201 vacuum line diagram suggests that there's a reservoir in the system. Thanks, Sixto 91 300SE 87 300SDL 83 300SD 
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#2
12-19-2002, 03:49 PM
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isn't the line running toward the fuse the vac supply
I am just guessing since my SDL is parked in the rain at home today, but isn't the VAC port on the amp connected to the main vac line that runs to the brake booster. I think there is a T from the big vac line to the vac amp inside of the sound barrier. There is also a locking line in there somewhere also.
As for the function of the vac amp, I kinda wonder myself... alec
__________________
84 300TD - 235k - Farbe "Surfblau" bought at 213k 87 300SDL - 131k - Farbe "PimpGold" bought at 115k 00 Klepper Faltboot Expedition Double
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#3
12-19-2002, 05:27 PM
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The only line off the big brake booster hose is the line to the key switch for the stop unit. The AT vacuum amplifier gets a vacuum feed, so to speak, from the a splitter at the AT vacuum unit on the IP.
I don't understand why there is a vacuum reservoir. To continue soft shifts after the engine cuts out? Sixto 91 300SE 87 300SDL 83 300SD
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#4
12-19-2002, 07:30 PM
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The shift feel control circuit is kinda complicated on the 603. Main vac supply is from the 5-way T at the vac pump (front of engine), and there is a vac reservior in there for some reason, probably to buffer the system rather than supply vac after the engine stops. Strange.
The vac amplifier controls the vac actually applied to the tranny modulator, and there is a circuit to soften the shifts with the engine cold. Also modifies shift under boost, too -- a good thing on this engine with the amount of torque it generates when the turbo comes up! Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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#5
12-19-2002, 07:46 PM
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Question here. When the car is cold, it shifts softer, so I know something is doing it's job. But recently, when I am under full throttle, the 1-2 shift is softer than usual, but light throttle produces a firm shift, how I like it. Any ideas?
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#6
12-19-2002, 08:30 PM
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Check the boost pressure line to the amplifier, and in fact the condition of ALL the connectors, I replaced all of mine. Some improvement (my complait was HARD shifts), but the real cure was to plug the lines to the EGR and Air recirc actuators, both were shot and leaking all the vac off.
Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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