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Unread 11-02-2011, 10:00 PM   #1
m0jo
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Center axle disconnect questions

I replaced my CAD motor today and have some questions about some things i noticed after the fact.

First, the CAD motor has a hexagonal head to it where it joins to the CAD housing that goes against a tab on the CAD housing to prevent it from rotating, my CAD motor's hex head is smaller than the old one and allows for some radial play but no axial play. Is the small amount it rotates okay? If not how would one stop it?

Second, When I start the Jeep in 2wd the CAD stays to the passenger side as intended, when I move the T-case to 4wd it moves to the drivers side, again, as intended, but when I put it back into 2wd while the Jeep is still running the t-case goes to 2wd but the CAD fork does not move back to passenger side until I shut off the engine and start it again. I'm assuming this is a problem with the vacuum switching mechanism on the t-case, to correct it do I clean the piece? replace it? Is it possible or even likely it could be caused by some form of leak?

Thanks guys and gals

regards,
Matt

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Unread 11-03-2011, 03:42 AM   #2
Mark05059
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try rolling a little when you take it out of 4x and see if it moves... if not then yes check out the switch on the transfer case.
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Unread 11-03-2011, 04:50 AM   #3
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Originally Posted by Mark05059 View Post
try rolling a little when you take it out of 4x and see if it moves... if not then yes check out the switch on the transfer case.
I agree. Also the smaller hex on the motor will not be problem. The motor shifts the fork laterally so the little rotation you might have wouldn't be an issue.
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Unread 11-03-2011, 06:06 AM   #4
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You can verify whether the transfer case mounted vacuum switch is working or not. Just manually check the vacuum lines going to the CAD and verify that when going back to 2wd the suction (vacuum) once again switches sides. If its pulling vacuum on the drivers side while in 4wd, but doesn't switch to pulling on the opposite side (passenger side) when engaging 2hi then you know your switch is failing to move vacuum from one side to the other.
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Unread 11-03-2011, 07:00 AM   #5
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I agree. Also the smaller hex on the motor will not be problem. The motor shifts the fork laterally so the little rotation you might have wouldn't be an issue.
agreed.

the shift collar will hold the fork in place no matter what.
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Unread 11-03-2011, 10:01 AM   #6
m0jo
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it was on jack stands at the time, tried rotating the wheel, kicking the CAD housing etc. The vacuum is holding it to the drivers side in the locked position.

The Vacuum not switching over was one of the original symptoms before changing the CAD motor, I have no clue how the T-case switch works so I figured maybe it needed some kind of back pressure or something to operate as the old CAD motor was blowing straight through and seized.

So the vacuum not switching over means the t-case switch is boned? What is it called to get a replacement and where on the T-case is it? Any dumb hardware on it like the safety torx on the idle air control motor?

EDIT: Also is there any difference between the 91 and 95 t-case?

Last edited by m0jo; 11-03-2011 at 10:20 AM..
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Unread 11-03-2011, 10:59 AM   #7
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I have no clue how the T-case switch works so I figured maybe it needed some kind of back pressure or something to operate as the old CAD motor was blowing straight through and seized.
The vacuum switch at the top of the transfercase is quite simple. It has 4 plastic tubes at the top to which you hook up your vaccum lines. It has a metal ball at the base of the threads that gets depressed when you engage the transfercase.

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Originally Posted by m0jo View Post
So the vacuum not switching over means the t-case switch is boned?
Yes, or that one of the lines coming from the switch has a leak and thus is not allowing vacuum to reach the CAD. Start with pulling the lines out and inspecting them. They are hard plastic, and crack VERY easily.
Before moving to a 1 piece cherokee axle shaft to completely elimiate the CAD, I replaced my lines with rubber vacuum lines from autozone/advance/etc... The rubber lines will last much longer IMO. So you could even start by replacing all of the hard lines. There is one that comes from the top of your motor and goes to the switch to supply vacuum. Then two go from the switch to the front axle.

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Originally Posted by m0jo View Post
What is it called to get a replacement and where on the T-case is it? Any dumb hardware on it like the safety torx on the idle air control motor?

EDIT: Also is there any difference between the 91 and 95 t-case?
1. Its called a "transfercase vacuum switch". They have them at autozone/advance usually in stock for about 15.00... It is part number: 49314 at autozone, they should be able to look it up directly. I can't post the link directly to the part at autozone's website because it will route you to their home page. If you go to the store and have them look up the part number or have them look up your vehicle make/year/modle and ask them for a: Transfer Case Switch


2. It is located on the passenger side of the transfercase near the linkage, it will have hard vacuum lines running out of the top of it. You will need to remove the lines to pull out the switch.


3. Kinda-sorta on the dumb hardware part... the switch is shaped kinda like a nut, to allow use of a very large socket to remove the switch. It does not take much torque to remove them, but you need a monster socket to fit over the switch. I recomend buying a socket to fit the switch when you purchase the switch at autozone/advance/o'riles/etc...

4. Not really any major difference between 91 and 95 other than a move from mechanical/electrical speed sensor assymblies to just electric.
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Unread 11-03-2011, 11:23 AM   #8
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Oh and by the way... if you ever get tired of dealing with vacuum switches, lines, actuators, and the entire idea of a CAD system, consider moving to a one-piece axle shaft out of a cherokee or TJ. This completely eliminates a need to engage anything other than your transfercase to achieve 4wd. It has no affect on drivability, your front driveshaft will spin all the time which some argue will discrese MPG but I argue that it is unoticable. My vacuum CAD system left me stranded on 2 seperate ocasions so I upgraded to a posi-lok system which is a manual cable version of what we have now, it failed as well and once again I was stranded. Now, with a one-piece axle shaft nothing needs to be done except engaging the tcase for 4wd.

Any year cherokee that is 4wd will work as long as it isn't an early cherokee that still had the CAD system. 92+ 4wd cherokees should all have no CAD system and a one-piece axle shaft.

It really is just as simple as pulling your CAD shafts out, installing a seal from Nappa Autoparts, and rigging up a block off plate to cover your old CAD opening (or you can just remove the fork and leave the stock cover on).

Below is a pretty good writeup on one-piece axle shaft conversions. It was done with a TJ one piece axle shaft but again an XJ (cherokee) shaft works too.

http://www.stu-offroad.com/axle/yjd30convert/yjconvert-1.htm
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