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Discussion Starter · #1 ·
This subject might have been covered already but here it goes.

Got an 87 rc but it won't go into 4wd. It'll shift there but the front tires won't spin. I wanna say its got the vacuum actuated lockers. But not sure. I'm tired of getting stuck in stupid places. So id like to get it working right. Are there diagrams for the vacuum lines out there on the web? Have done google searches but no luck. Thanks for the help.

Josh
 

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I had this problem, only in reverse. I would be able to shift just fine into 4WD but couldn't for the life of me shift out of it.

My issue was the vacuum lines running from the t-case to the CAD unit located on the driver side of the front axle. There's two lines there. One of them pulls a vacuum to lock the CAD into 4WD and the second vacuum lines pulls a vacuum to unlock it 4WD. Replace those and that should do it.

http://ramchargercentral.com/vehicle-help/cad-pictures-and-links-to-the-faq/
 

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You need to search for CAD (Central Axle Disconnect) on this site.  Could be a bad vacuum actuator on your front axle.  Also need to check your vacuum lines as well.
When the 4WD wouldn't engage on my old 87, it was the actuator.
 

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Discussion Starter · #4 ·
Cool, I will check that trash out when I get a chance. I know I'm missing some vacuum lines so I gotta figure out where they go.
 

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There should be a vacuum diagram sticker on the underside of the hood. Don't know if yours is still there but mine is. I can take a pic of it if you need me too.
 

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You can also 'lock' the CAD and put on some lockout hubs as well.  I believe there's a thread in the 'how to' section on this.
 

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cjohhny said:
You can also 'lock' the CAD and put on some lockout hubs as well.
But then you need to get out of the nice warm dry truck to lock the hubs in if your out drivin around come winter and get stuck. I thought of doing this as well but decided I like staying warm and dry in the cold. Not to mention I'm lazy and shift on the fly appeals way to much to me.
 

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dgabajay said:
But then you need to get out of the nice warm dry truck to lock the hubs in if your out drivin around come winter and get stuck. I thought of doing this as well but decided I like staying warm and dry in the cold. Not to mention I'm lazy and shift on the fly appeals way to much to me.
If you think you will, or even might, get stuck, lock the hubs before leaving the house or pavement.

Trying to figure out the vacuum line routing for the CAD is a pain in the rear. I have two Dodges with a CAD and had problems with both. I "permanently" locked the CAD, which is something easily done, and added a set of lockout hubs. Some people like to make it sound like it takes forever to get out and lock the hubs in but it only takes maybe a minute at the most. A little pre-planning and having to do it in mud or deep snow can be avoided. I have driven all winter with my hubs engaged and never noticed a decrease in mileage or an increase on wear in anything.

Chris
 

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This switch is very likely the culprit as Mojack mentioned.

To diagnose it:
First, pull both vacuum hoses off the CAD motor. Start the truck and let idle while in 2wd. Crawl underneath and note which vacuum line has vacuum. Now, go shift into 4wd (still idling). Crawl underneath again and see if the vacuum moved to the other vacuum line.

If it did move to the other line, your switch is fine and maybe you should start checking for cracks/damage to vacuum line and vacuum ball.

If the vacuum didn't switch to the other line, your t-case switch is bad. The switches are relatively cheap, but are a pain to replace.
 

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Discussion Starter · #11 ·
Finally got under the truck today. Looks like a couple lines arfe cut. But I could be wrong. I'm probably just gonna swap for locking hubs. There aren't any stickers on the truck aside from the doorjam one. I don't care for shift on the fly anyway.
Josh
 

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Manual hubs do nothing for you unless you lock the CAD on the axle.  And you'll still have to shift the transfer case in/out of 4WD.
If you've got cut vacuum lines, why not repair them and move on? 
 

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Discussion Starter · #14 ·
Ok, so I think what I'm gonna do is convert it from vacuum controlled to a manual controlled cad. Here is the kit I have found.

http://4x4posi-lok.com/app_dodge.html

Looking at it and some pictures of the cad actuator, it looks like you could just get a cable, modify some parts, and voila, you got yourself a manual locking cad. But that's just my theory. Please, correct me if I am wrong.

Josh
 
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