Testing the 4wd vacuum switch system? - JeepForum.com
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post #1 of 16 Old 05-11-2013, 08:33 PM Thread Starter
jred
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Testing the 4wd vacuum switch system?

I've been searching the forums for a couple of days, but I guess my search-fu is weak.

New to Jeeps, new to 4wd, but not new to automotive/motorcycle mechanics. '94 YJ Sahara, mostly stock from what I can tell (except apparently a PO did the 20 gal tank "upgrade"). It's a DD, but I'd like the option to do some light wheelin' if the bug decides to bite.

Shifting into 4H doesn't do anything, shifting into 4L changes the gearing, but still no front drive. The front drive shaft spins, though. I called myself testing it before I bought it, but being a 4x4 newbie, the gearing change threw me off. I've since tested it on loose dirt, and the front axle is definitely not getting power. I know the "right" thing to do is go with a posi-lok & do away with the vacuum system altogether, and if I need to I will, but I'd hate to put the time & money into it if it's a simple vacuum line or fitting that can be replaced.

So *is* there a thread that I've missed that details how to test the stock system? I visually checked the vacuum line coming off the intake and the dual-looking fitting that goes into the vacuum switch (? circular bit on the passenger side of the front axle), and it "looks" ok, but looks can be deceiving.

Thanks for any info you can pass along.

PS: After doing the little things that should have been done before I bought it (117k miles & stock plugs, wire, dist cap & rotor???), I'm loving it! Took the hardtop and full doors off today and both my 14yo daughter and my German Shepherd thought it was the coolest thing ever!

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post #2 of 16 Old 05-11-2013, 10:20 PM
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post #3 of 16 Old 05-11-2013, 11:44 PM Thread Starter
jred
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Ah, thanks. I somehow saw & saved the pics and totally forgot the text. The first time I read it, what I comprehended was "the lines are probably shot, replace them. There are a couple of switches and a motor that may also be bed, replace them if the lines don't fix it." What I completely missed was "if your indicator light doesn't come on, it's most likely a vacuum issue."

Oh, well. Nothing to it but to do it, I guess
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post #4 of 16 Old 05-12-2013, 09:07 AM
disarm6565
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If you're going to spend ANY money on the vacuum system, also search "DIY Posi-Lok" and "TJ Axle Shaft Upgrade." I've had all 3 and now have the TJ Axle shafts and haven't looked back.

1993 4.0 AX-15
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post #5 of 16 Old 05-12-2013, 09:19 AM
Anticanman
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Or you can lock the fork over and be done with the vacuum system.

http://www.jeepforum.com/forum/f12/t...80/?highlight=

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post #6 of 16 Old 05-12-2013, 12:42 PM Thread Starter
jred
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It's primarily a street jeep, so I don't want to lock it permanently. IIRC, that's bad for the TC.

I saw the DIY posi-lok, but I don't trust myself with a tap & die. That stuff always comes out wonky for me :P
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post #7 of 16 Old 05-12-2013, 12:49 PM
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It's not bad for the TC. Mine is mostly a street jeep and its fine.

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post #8 of 16 Old 05-12-2013, 01:38 PM
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Nothing wrong with the vac system, mine has worked since 88 with only minor maintenance to keep it working as designed.

Dwayne
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post #9 of 16 Old 05-12-2013, 02:39 PM Thread Starter
jred
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I found a decent write-up for testing on wranglerforum. http://www.wranglerforum.com/f8/how-...ems-17802.html

If linking to other boards is a no-no, let me know or mods can delete. Just posting it here so the next guy looking can find it.
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post #10 of 16 Old 05-12-2013, 05:12 PM
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If yours is bad I just pulled mine off and replaced it with a steel plate when I upgraded to XJ shafts. Let me know if you want it, still works just fine.

91 YJ, 350/700R4/231, 8.8/HPD30 with 3.73s, 6" SOA with 38" TSLs. If I ever see the previous owner again, I am going to curb stomp that meth-head brain dead crackpot.
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post #11 of 16 Old 05-12-2013, 08:24 PM
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post #12 of 16 Old 05-13-2013, 06:27 PM Thread Starter
jred
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Thanks, I hope to get to check it this weekend.
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post #13 of 16 Old 05-13-2013, 08:28 PM
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Does anyone know if there is a 4x4 light in a 90 with a 4 banger base model?
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post #14 of 16 Old 05-13-2013, 08:32 PM
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There's a 4x4 light on all YJ's. if you have a clock, the light is illuminated in the Star Trek panel above the steering wheel. If yours didn't come with a clock, the circular gauge in the center bezel closest to the steering wheel will illuminate.



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post #15 of 16 Old 05-13-2013, 08:47 PM
litone12
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Haha star trak panel awesome! I know my 4x4 does not work thanks! Just wasn't sure if it had a light for it. Is there a wrong way to put the vacuum lines on the tc? J/w because my jeep needed a new trans before I could drive it.
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