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#1
09-26-2004, 11:07 PM
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450SLC - Transmission Won't Kick Down (Bad Solenoid??)
I have a 1977 450 SLC. The transmission was working great until a few days ago when I tried to floor it, and it didn't kick down. Since then I haven't got it to kick down at all. The transmission still works fine and shifts through all gears, and you can still shift down with the shifter.
I checked the Kick down switch under the gas pedal and it was working properly. Where the wire from the kick down connects to the transmission; there's power when the switch is down. I located the kickdown solenoid on the transmission, and when the KD switch is down the solenoid clicks. I removed the solenoid from the transmission. I tested using a 12V battery; when I applied power the solenoid clicked, and a rod or pin moved down slightly. Does anyone know if that's what it is suppose to do? If it isn't the solenoid could it be anything else, or is the transmission itself in trouble? I looked online to purchase a new solenoid, but I couldn't find anyplace that sells one. All I could find was the seal for the solenoid. Do I have to buy this from Mercedes? Any suggestions on how to fix, or where to buy the part would be greatly appreciated. THANKS! 
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#2
09-27-2004, 08:49 AM
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Possibly relavent, possibly not. Watch out for your fuel pump. It might be on its way out, especially if it has not been replaced recently. If you do replace your fuel pump(an easy job) make sure you get a new fuel filter at the same time. Fuel pump ~$180 filter ~$20.
I had no kick-down in my '78 208E(same Bosch K-jetronic CIS) unless I really stomped on it. Shortly afterwards my fuel pump failed. Sorry I can't help with the specific transmission question. I'll be interested in other, more knowledgable replies. Alex
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'78 W123 280E, 58,000 mi! '97 Mazda Miata '94 Isuzu Trooper, 4WD '03 MB C240 4-matic Wgn - Wife's From the Archives: '73 2002 '68 TR-250 '67 Austin Cooper "S" '59 Austin Seven (Mini) various p'up trucks
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#3
09-27-2004, 06:55 PM
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Thanks for the info. I don't really think it has to do with the fuel pump. Before about a week ago the car kicked down great, every time. Now it will not do it at all, even if I hold pedal to the floor for a long time. Could it have to do with the transmission modulator?
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#4
09-28-2004, 08:36 AM
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On this model, it's a straight circuit from the fuse through the switch to the solenoid.
The solenoid is supposed to activate a kick-down valve. Sounds like either the valve is bad, or the solenoid is not moving it enough. There were some posts on this a while ago.
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Chuck Taylor Falls Church VA '66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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#5
09-28-2004, 06:44 PM
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Quote:
If the valve is bad, is there anyway to fix or replace w/o getting a whole new transmission?
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