73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: David Hall on February 26, 2009, 04:10:53 pm
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86K10
305
700R4
NP208
Can anyone identify this vacuum switch? The wires going to it are lt. blue and yellow? What does it control in the transmission?
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I can't post pictures, File too large?
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e-mail the file to yourself and select "make image smaller", or post the picture on photobucket and put in a link.
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This is a how to on shrinking a picutre small enough to upload to the forum using Microsoft paint.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=6428.0
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Dave, Is it on the firewall above the right valve cover?
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No, I just modified my first post with the smaller pics.
Take a look.
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That doesn't look like a vacuum switch.
Where are those wires running to?
They must have something on either end.
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It has two hard plastic lines going in. And in the picture the wire connector has been unplugged
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I believe that is the EGR Bleed Solenoid.
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It pulls vacuum from a thermal vacuum switch on the front of my intake (not on the thermo housing) and also from the back of my carb. It does connect to the egr but the wires from the switch are part of the harness that connects to my transmission plug (pin D) yellow wire.
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Read this. I don't know the wiring harnesses intimately but I identified the solenoid off the emissions decal under my '86 hood.
http://www.asashop.org/autoinc/dec97/egr.htm (http://www.asashop.org/autoinc/dec97/egr.htm)
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Not trying to troubleshoot the egr, I'm trying to find out what this switch controls in the transmission. Thanks for the link though. I figured out this much so far: power comes from brown wire off the fuse panel, goes through the brake light switch on the pedal and comes out lt. blue. The lt. blue wire (hot),lt. blue wire w/black stripe and green wire (dianostic) go through the firewall and connect to another harness. This new harness, connects to the low pressure vacuum switch behind the brake booster, vacuum switch in picture and on to transmission connector. Question is what does vacuum switch in picture (on right valve cover) have to do with my 86 700R4.
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The other end goes to the TCC solenoid.
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On the transmission plug I have three wires (Green / A, Lt. Blue / B and Yellow / D). In side transmission Yellow goes to TCC.
Lt. Blue wire is from my low pressure vacuum switch, any idea where it goes in the trans.
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So the transmission has two vacuum switches for the TCC?
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(http://i6.photobucket.com/albums/y228/Sabaka454/tcc-1.gif)
Image restriction direct link here (http://i6.photobucket.com/albums/y228/Sabaka454/tcc-1.gif)
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Thanks Vile for the help. The vacuum switch in my first post is the EGR bleed sol. I found out that it keeps the TCC from locking up via. a TVS until the engine reaches appro. 170 deg. To remove the bleed sol.,vacuum lines and tvs. I need to find a 170 deg. temp. switch or some other way. When retro fitting the trans into earlier muscle cars wonder how they did this.
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Just bypass it all together then. The converter can lock and unlock at any temp without any problems.
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After thinking about it I think I am going to connect the two wires toghether for now. I would like to make it lockup only in 4th though. I will do some light towing. Here's a pic of the valve body, which switches control which gears?