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-   -   4x4 vac leak? (http://www.ramforumz.com/showthread.php?t=145028)

98rumblebee 06-14-2013 09:19 AM

4x4 vac leak?
 
When I bought my truck about a month ago, I was told that the 4x4 won't engage due to a vacuum leak/problems with vac lines. Everything else this guy told me checks out so I believe it, the problem is I really don't know shit about transfer cases or vacuum lines. Can anybody point me in the right direction as to where I should be looking? Are there any special procedures to replace vac lines?

RogerRamJet 06-14-2013 09:38 AM

I believe he is talking about the vac line that runs to the front axle/differential. I believe Dodge still used vacuum to engage the locking mechanism for 4WD then. Check on the rear side of the diff/axle for a loose, broken vac hose.

98rumblebee 06-14-2013 11:10 AM

Thanks I will do that and get back to you

Warlock III 06-14-2013 11:57 AM

I concur. There should be a green and a red (hard plastic) vacuum line running down to the front axle from the passenger's side of the truck (probably too close to the exhaust).

It engages the actuator inside of the axle on the passenger's side rear of the front axle. Pull of the double connection on the back of the actuator and check for vacuum.

98rumblebee 06-16-2013 09:26 AM

Do I need a tool to check for vacuum or just kinda stick my finger on there and see if it has suction?

In case it matters the 4x4 light is always on no matter what position the transfer case is in. Can't find neutral on the transfer case either.

Wh1t3nukle 06-17-2013 09:44 AM

Warlock, his being newer than yours I think his line color to the CAD is Black and Red. Mine are on my 2000.

98rumblebee -- see this link for greater info to learn about the 4x4 system. http://dodgeram.org/tech/repair/4X4/4x4_engagment.htm

If the light is "RIGHT", then that means it's always engaged, the shift collar is locking the passenger axle.

Here is a picture of mine for reference, where the connection is on the axle. See the broken red wire? The union there that both lines are going into is what Warlock is suggesting to pull off.


http://i150.photobucket.com/albums/s...ps5ff47f73.jpg



With truck running, put your finger to either hole to feel any vacuum being drawn.

If you don't feel ANY vacuum on either line, then you have hole/leak somewhere else in the system.

98rumblebee 06-19-2013 07:34 AM

Alright here's what I can tell you:

My setup looks like the one in the above picture. The black line has suction and the red does not. This is true for both 2H and 4H. When the lines are disconnected, the 4x4 light goes off.

Do I just need to replace that red line? 4x4 is definitely not working, even though the light is on.

Wh1t3nukle 06-19-2013 09:48 AM

Quote:

Originally Posted by 98rumblebee (Post 1129579)
Alright here's what I can tell you:

My setup looks like the one in the above picture. The black line has suction and the red does not. This is true for both 2H and 4H. When the lines are disconnected, the 4x4 light goes off.

Do I just need to replace that red line? 4x4 is definitely not working, even though the light is on.


So it seems to be working correctly. The black line is responsible for engaging the fork (4wd). I know this b/c (accidentally) my red line broke unknowingly on a trail and I was still able to get in and out of 4wd. My light was not operational b/c I disconnected the connection for that as it was too short for the axle droop amount.

In short, you have to get the red line connected. If yours broke like mine, then you'll have to buy a new vac harness, which I had to do. If your break is upstream (away from that union), then you can get some vac adapters to close it up.

I ordered the harness part from autopartsasap.com, but they are NOT ASAP. Ordered on May 23 and received May 31.

Mopar 52105299AB Vacuum Front Axle Harness for $31

Here is what you get:

http://i150.photobucket.com/albums/s...ps41a7b61d.jpg



I then decided to EXTEND the line to not break it again.

Picked up some unions and such from AutoZone

http://i150.photobucket.com/albums/s...psa0bc439d.jpg


My hard lines were fine, so keeping that for spare.


http://i150.photobucket.com/albums/s...pscf5ada92.jpg


http://i150.photobucket.com/albums/s...psa058ab8b.jpg



Hopefully will sell this axle sometime this year.

98rumblebee 06-19-2013 10:43 AM

No visible breaks anywhere, but enough rust that I figure there's either some real small holes or something on the back of the hard lines that I can't see. Only thing I'm confused about, your description makes it sound like it would be stuck IN 4x4 and not out. Not that I'm complaining, this stuff is just hard to visualize.

Wh1t3nukle 06-19-2013 11:18 AM

Correct. It would be in 4wd. If yours is not, then either the vac on the black line is not strong enough to pull the collar or there is something preventing the collar from fulling engaging.

You just need to generally inspect everything related to the CAD. Did you read the earlier link I posted about the system?

Unplug the soft lines that goes to the hard lines on the frame. With truck running, confirm there is vacuum there, just like you did on the axle end. Follow the hard lines to the tcase and visually check. Clean it up. Maybe have a squirt bottle with soapy water to spray.


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