What is the Blue vacuum line?

Bronco · Jun 29, 2004

:dunno: I have disconnected the Vacuum lines that run back to my Tcase because my new Tcase doesn’t have a provision for them. So my plan is to use an FSJ center dif Vacuum switch like this http://www.buildyour4x4.com/BY-Tech/QT-Tech.html inside the cab to control the dif locker. The problem is, in an effort to figure out what was what with those vacuum hoses I have hit a blind ally. So far it looks to me like the Red one goes right to the manifold so it is the source of suction. When I use a short piece of hose to connect Red to Yellow the axel locks and the dash light comes on. If I hook it to green it disconnects the axel and the dash light goes out. The blue one doesn’t seam to do anything when I connect Vac to it. So I followed it and it just ends into a little plactic disk and I can suck and blow air through it so what dose it do? Is it supposed to be hooked to something (there is a nipple on the other side of the disk) or is it just the relief to the system so that when you take Vac off, say yellow the air can get in and let in shift. Anyway my system seams to have a leak because the AC cuts out on me when the engine is pulling hard (see: http://www.naxja.org/forum/showthread.php?t=27612 ). So if I have RED connected to Green and yellow open to the air do I have a leak? I know Blue is not my leak because I found both ends and neather are connected to anything right now. Who knows how this all works? Help! Thanks

ChuckD · Jun 29, 2004

Bronco said:
:dunno: I have disconnected the Vacuum lines that run back to my Tcase because my new Tcase doesn’t have a provision for them. So my plan is to use an FSJ center dif Vacuum switch like this http://www.buildyour4x4.com/BY-Tech/QT-Tech.html inside the cab to control the dif locker. The problem is, in an effort to figure out what was what with those vacuum hoses I have hit a blind ally. So far it looks to me like the Red one goes right to the manifold so it is the source of suction. When I use a short piece of hose to connect Red to Yellow the axel locks and the dash light comes on. If I hook it to green it disconnects the axel and the dash light goes out. The blue one doesn’t seam to do anything when I connect Vac to it. So I followed it and it just ends into a little plactic disk and I can suck and blow air through it so what dose it do? Is it supposed to be hooked to something (there is a nipple on the other side of the disk) or is it just the relief to the system so that when you take Vac off, say yellow the air can get in and let in shift. Anyway my system seams to have a leak because the AC cuts out on me when the engine is pulling hard (see: http://www.naxja.org/forum/showthread.php?t=27612 ). So if I have RED connected to Green and yellow open to the air do I have a leak? I know Blue is not my leak because I found both ends and neather are connected to anything right now. Who knows how this all works? Help! Thanks

Dude, work a different font, and double space. This thread sucks! :rattle:

Bronco · Jun 29, 2004

ChuckD said:
:rattle:

woody · Jun 29, 2004

It's been a few (peaceful) years since I fooled with the sucky vacuum axle setup, but IIRC the shift motor connects/disconnects the two r/s axles by vacuum applied in opposite directions:

in 2WD, the vacuum sucks the fork/collar to the pass. side (uncoupling the splines)
in 4WD, the vacuum sucks the fork/collar to the driver's side (coupling them)
A third vacuum line 'tells' the "Part Time" dash light to come on.

All ya gotta do is rig that switch to do like the above, and you are golden

Probably 'tee' off the side that engages the splines so it lights the light... or simply forget the light.

My originally 242 jeep with swapped in vacuum 231 has no provisions to light the lights... I just assume that when the lever is all the way back, things aren't grinding a pound, and it goes when I gas it, it's in 4-Low. I have absolutely no need for 4-High, but if I did, I'd put the lever into that spot where it's not in 4 Low, neutral, 2-High, or grinding :dunno:

Bronco · Jun 29, 2004

I had heard that the third (blue) line was to turn on the Light but when I hook Red to Yellow I get the light and the axel is locked with the blue still exposed to air. So I don’t think that’s what the blue is unless I have really screwed things up and I don’t think I have yet. Like you I could do without the light but I want to know what is going on with the leak before I start thinking things aren’t important. Thanks for the help.

woody · Jun 29, 2004

You could find a shop with a smoke generator...those things are great for finding vacuum & exhaust leaks.

What is the Blue vacuum line?

Bronco

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ChuckD

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Bronco

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woody

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Bronco

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woody

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