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Unread 09-21-2012, 08:35 AM   #16
proFISHent
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is the ride any different if I were to go permalock than if I go posilock? I am refering to when I am in 2 wheel driving on the street. does it affect mileage or anything?

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Unread 09-21-2012, 10:11 AM   #17
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Is mileage really something you're worried about when you strap knobby tires to a brick with a sail on it? The front driveshaft will spin when in 2wd but if you get it balanced then there will be almost zero indication that you've done the modification.
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Unread 09-21-2012, 02:29 PM   #18
tchoberg
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proFISHent - Should you wish to repair your 4x4 vacuum system please take a look at this link. http://oljeep.com/87_yj_4wddiagram.jpg

I found this a while ago and it helped me troubleshoot the 4X4 system on my 87 YJ and I found the system is simple as dirt. No mysteries.
My problem was a broken vacuum line which I spliced using a short piece of windshield wiper hose. Cost? -0-.
Since then, my 4x4 system has operated every time since and I have found it to be 100% reliable in sand, mud, and snow for the last 2 years.
I don't have anything against a posi-lock other than the price and the need to do two things to do when you want 4x4 operation rather than one thing to do with the vacuum system.

A few troubleshooting hints if you decide to go that way;
The vacuum switch is located on the top of the transfer case and has 4 hoses, which are;
1. Blue - goes only to the Vent/Check valve. (Mine sort of hangs loose but I tie-wrapped it one of the other hoses)
2. Green- goes to one side of the CAD on the front axle.
3. Yellow-goes to the other side of the CAD on the front axle.
4. Red-this is your vacuum pickup and goes to the manifold . (This was what I repaired with the windshield wiper hose)

Black hose- goes from the CAD to the 4x4 switch on the firewall. (I think is a dual line with the yellow line in sort of a dual connector - its been a while)

The yellow line is tough to see on the link diagram but it goes from the switch on top of the transfer case to the CAD. ( see #3 above.)

I used a brake bleeding hand vacuum pump to test the CAD (vacuum actuator) on the front axle. Hook the pump to one side of the CAD and then the other side to see if the CAD moves in and out or leaks.

See - the system is simple as dirt with no mysteries if you have a diagram, theory of operation, and where the parts are located.

Hope this helps - yours could be a zero fix also.
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Unread 09-21-2012, 03:26 PM   #19
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anticanman its not my first consideration but I always believe weighing the options is a smart approach. If both the posiloc and the permaloc run simmilarly but one gets 1 or 2 mpg better than the other, why would I choose one over the other.

Like I said, this is completely new to me. I have an 03 chevy Duramax on 6 inches and 35s that is my daily driver. Its expensive to run and crazy expensive to repair. I am looking for something reliable and relatively cheap compared to what I have so mmy wife and son can go to the woods with me and so I can take hunting and not worry about beating the hell out of it.

tchoberg, I REALLY appreciate the thread attachment. If you dont mind me asking, why would you choose something with vacuum lines over something like the posi/perma lock where you dont have to worry about loosing the vaccum? I am just worried if I am way out in the woods and i vaccum line gets caught on something or gets dry rot and I am screwed! Its another option I need to weigh in though for sure. cheaper is my favorite lol.
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Unread 09-21-2012, 03:52 PM   #20
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The posilock has proven itself to be unreliable to some users. The tj came with a solid passenger axle shaft so what's wrong with your Yj having one?
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Unread 09-21-2012, 04:01 PM   #21
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I just ran my vacuum source from the manifold i have no vibs or problems
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Unread 09-21-2012, 04:06 PM   #22
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Quote:
Originally Posted by Anticanman
The posilock has proven itself to be unreliable to some users. The tj came with a solid passenger axle shaft so what's wrong with your Yj having one?
The posi luck was more unreliable than the vacuum...

I agree, if the vacuum was such a good thing why did it go away in the next generation vehicle?
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Unread 09-22-2012, 10:38 AM   #23
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Quote:
Originally Posted by Anticanman View Post
The posilock has proven itself to be unreliable to some users. The tj came with a solid passenger axle shaft so what's wrong with your Yj having one?
this is exactly the information I am looking for. Like I have said, I know NOT A THING about jeeps, in fact I dont work much on vehicles period. It was my understanding that is what these forums are for, to ask questions if we dont know. No matter how stupid the question sounds.
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Unread 09-22-2012, 10:39 AM   #24
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are there any negatives, or drawbacks to the permalock?
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Unread 09-22-2012, 10:42 AM   #25
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Quote:
tchoberg, I REALLY appreciate the thread attachment. If you dont mind me asking, why would you choose something with vacuum lines over something like the posi/perma lock where you dont have to worry about loosing the vaccum? I am just worried if I am way out in the woods and i vaccum line gets caught on something or gets dry rot and I am screwed! Its another option I need to weigh in though for sure. cheaper is my favorite lol.
My 4X4 vacuum system has served me well since my $0 repair and I have been offroad in woods, desert, and in the snow many times and never had a failure. I like the fact that I can pull the transfer case shifter into 4X4 mode and its done without having to do 2nd function to get there.

Plus I guess I'm cheap and would only go to the other system if I had to put out a lot of cash to get the vacuum system to operate.
Like I said earlier, it is a dirt simple system and I would give troubleshooting it a shot to see how much money would be needed to get it to work. You may be surprised.
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Unread 06-13-2013, 11:05 AM   #26
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This thread is an epiphany! Eureka!! I got my jeep stuck in a ditch thinking: what the hell, it's a Jeep what could go wrong. Since finishing it, I have really been off road yet. Wow, I had to be pulled out by 2 dudes and a John Deere Gator with a winch. Humbling to say the least. Well I didn't realize that the front axle wasn't locking until..you guessed it, I got stuck. Turns out the red vacuum line in the diagram was removed on mine when the previous owner did the Offy conversion...some people's kids! Anyway going to fix'er up this weekend, should work 4.0, already checked the vacuum do dad on the axle with a brake bleeder kit and it holds pressure. Thanks!!!
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Unread 06-13-2013, 12:25 PM   #27
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Quote:
Originally Posted by 1987_yj
This thread is an epiphany! Eureka!! I got my jeep stuck in a ditch thinking: what the hell, it's a Jeep what could go wrong. Since finishing it, I have really been off road yet. Wow, I had to be pulled out by 2 dudes and a John Deere Gator with a winch. Humbling to say the least. Well I didn't realize that the front axle wasn't locking until..you guessed it, I got stuck. Turns out the red vacuum line in the diagram was removed on mine when the previous owner did the Offy conversion...some people's kids! Anyway going to fix'er up this weekend, should work 4.0, already checked the vacuum do dad on the axle with a brake bleeder kit and it holds pressure. Thanks!!!
Don't fix it. It is unreliable. I fixed mine a few weeks back it worked for 2 runs. Then it stopped working again ( mine holds pressure also ) I removed the the fork on the actuator cut a shock bushing sleeve down put that on the shaft for the actuator and reinstalled the fork and e clips. Now my front says engaged all the time.
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Unread 06-13-2013, 03:11 PM   #28
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Does grab or chatter when you make turns?
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Unread 06-13-2013, 03:24 PM   #29
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Does grab or chatter when you make turns?
There's a big difference betwixt "locked cad fork" and "locked differential". The cad fork turns it into a faux one piece shaft like the later Cherokee and tjs.
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Unread 06-13-2013, 03:53 PM   #30
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Does grab or chatter when you make turns?
It did at first but that's cause I had a bad u joint and hub. Now that I replaced both of those it is quiet and you can not tell the cad is locked at all.

Nick is right it's completely different then a locker I basically bypassed the cad vaccum system.
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