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87 Dodge mountian goat
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Discussion Starter #1 (Edited)
Hi....I'm new here so bear with me. I have a 87 Dodge W250 3/4T 4x4. I live way up in the mountians and am in about 2 foot of snow. This mornin i was on my way to work and my 4 wheel drive quit workin...I know it's the CAD unit. Is there a way to jerryrig it so it's locked in untill I can get the Posi-loc setup. plz help i'm currently snowed in because of this. I have already checked the vacuume to the actuator and i'm getting really good vacuume.
 

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Have you checked the diaphram? If you have a vac pump you can check it to see if it holds vacuum. Im going to look at my spare and see if there is a way to rig it. Be back in a minute.
 

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87 Dodge mountian goat
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Discussion Starter #3
i don't have a vacuume pump but once i get the actuator out, being's i know i have good vacuume...i'll hook it back up to the line's and see if it move's

waiting for your idea lol
 

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The only thing I can come up with (other than replacing the diaphram) is to take off the C-clips holding the diaphram shaft and fork in the housing, then remove i from the housing and add enough washers on the shaft as you put it back in to keep the fork in the engaged position. I just took mine apart and thats the only thing I can come up with. If anyone else has some ideas, please help this guy out! Oh by the way, some Jeep Wranglers have the EXACT same CAD as our Dodges!!!
 

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87 Dodge mountian goat
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Discussion Starter #5
Gonna go give that a shot. I'll let you know in a few how it works.......I HATE SNOW lol
 

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Same Name, Different Game
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While I have no way of helping you, I have to subscribe to see if you got yourself out of your house.
 

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Just be sure when you put it back in that you slide the collar on the axle over to the engaged position and line up the fork. Just so you know, Ive never done this before. It does look like it would work though.
 

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87 Dodge mountian goat
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365 Posts
Discussion Starter #10
came in real quick to grab more coffee and warm up (it's really cold)...it's about halfway out. Not alot of wiggle room under there. i'm probably gonna have to jack up the front end to get the collar liked up huh....is it springloaded
 

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87 Dodge mountian goat
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Discussion Starter #11
i "think" the problem might be the vacuume pot....i'll know in a sec
 

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It usually is the vac diaphram "pot" that starts to leak and wont hold the collar in the engaged position. Does the 4wdrive light come on at all?
If the diaphram hold vacuum, try what Threetwos said and flip the vac lines. Only one at a time should have vacuum. One while in 2wd and the other in 4wd.
 

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87 Dodge mountian goat
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365 Posts
Discussion Starter #13
OK...this is what i've fount out so far. I got the fork pulled out. I had my wife start the truck and shift from 2WD to 4WD and back. When she shifted i could feel and heart a slight clunk inside the dashpot. When i disconnected the lines one "whooshed". Telling me it held vacuume. so i'm thinkin that the diaphram is ok just something is awry in the linkage. also the fork and the rod it's attached to won't move...it's tighter than a knat's ass. SO were should i go from here
 

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So you got the diaphram and housing off of the axle? If so, hook up the vac lines to it and watch the fork for movement. If it pulls the fork to one side AND holds it then it should be working. If I remember right, the collar that the fork engages on mine was pretty tight and I had to work it back and forth to get it working. Has it been a while since you have used the 4wd?
 

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Just found this! Good explanation of the system!

Message:
Take a look at this image,

http://www.walt-n-ingrid.com/0X280010.jpg

My truck has a lift kit so yours will look slightly different. Look at the
connection just behind the tie rod end in the image. If the end of the wire
looks like this then it is the wire for the 4WD lamp in the cab. It's a
plug with 2 wires that connects directly to a switch on the front axle. The
front axle has a Central Axle Disconnect or CAD. The CAD works sort of like
an automatic hub and on an 87-90 Dakota works completely by vacuum. There
are two vacuum lines that connect to a small round canister on the front
axle that looks kind of like two small pie tins pressed together. You can
see it on the left side of this image.

http://www.walt-n-ingrid.com/0X150003.jpg

The other end of the vacuum lines run to a switch on the transfer case. If
you look under the truck, you'll find it to the rear of the transfer case on
the driver's side of the truck. It will have 4 vacuum lines connected to
it. Two lines for the front axle, one from the engine and one to a ball
canister connected to the underside of the bed.


All the wire with the plug on the front axle does is turn the 4WD lamp on
and off. It is very common for the vacuum actuator on the front axle to
stick.


Here's how to test it:


Disconnect the two vacuum lines from the front axle. With the truck running
and in two wheel drive you should have vacuum to only ONE of these two
lines. Make a note of which line has the vacuum. Now shift the truck into
4Hi and recheck the lines. The vacuum should change to the OTHER line. If
it does not, the switch on the transfer case is bad and should be replaced.
If I recall correctly, it will cost around $30-$40 at the dealer. It's kind
of like an oil pressure sending unit and will screw into the transfer case.
It has a small metal ball on the threaded end and when the transfer case is
shifted into 4WD, something inside the transfer case pushes in the metal
ball and changes the valve inside the unit.


If the vacuum does change from one line to the other, the actuator on the
axle is stuck. Like I said earlier, this is very common. You can try to
loosen it up by spraying some WD40 into each vacuum tube the lines connect
to. Don't be shy, really try to flush the crud out of it with the spray.
Reconnect the lines and drive the truck forward shifting in and out of 4WD.
Repeat the process rolling backwards. If it doesn't come loose, you will
have to replace the actuator. Once it is working, repeat the flushing
process about once every six months to prevent it from happening again.


Remember, if the wire is disconnected, the 4WD light will not come on.
There has to be a reason why someone disconnected it. Watch for blown fuses,
unusuall power drains, etc.. Also, sometimes when in 4WD, if you shift back
into 2WD, the front actuator will stick. Usually happens in cold weather.
The transfer case will be in 2WD but the CAD is still locked and the 4WD
light will stay on. Shift the truck into reverse and back up about 15-20
feet. That will usually pop it loose when stuck locked.


Walt Felix
88� Dakota Sport 4x4
http://WWW.Walt-n-Ingrid.COM
 

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87 Dodge mountian goat
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365 Posts
Discussion Starter #16
i'm workin on getting the vacuume pot of the housing...what a pain. I use my 4wd everyday. I live WAY back in the mountians. use 4x so i don't tear my tires up in the summer..and winter. have to have 4x and full chains all around.

I got all the e-clips out (3). Vacuume pot should come right out...right
 

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87 Dodge mountian goat
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365 Posts
Discussion Starter #18
got the vacuum pot out. i'n lookin at tha rod i thinkl it's slightly bent
and it was binding up in the bore's...now what lol. sorry for the spelling...typing with gloves on
 
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