Vacuum Disconnect Front Axle

Hey I have a 91 4.0L AW4 N231 (i think), and I have a question for all of you. It has the vacuum disconnect front axle, and I don't think it's engaging the axle or something. The front driveshaft spins when in 4-Hi (4-Lo gearing works too), and the little diaphragm is getting vacuum when it is in or out of 4wd. Could that little plunger/draphragm thing be clogged up? Is there anything else I should look for before taking it apart? And would anyone happen to have a picture of what one of these looks like taken apart and what I should clean/ look for thats broken? Thanks a bunch, if you need anymore info lemme know.

MoparManiac said:

Hey I have a 91 4.0L AW4 N231 (i think), and I have a question for all of you. It has the vacuum disconnect front axle, and I don't think it's engaging the axle or something. The front driveshaft spins when in 4-Hi (4-Lo gearing works too), and the little diaphragm is getting vacuum when it is in or out of 4wd. Could that little plunger/draphragm thing be clogged up? Is there anything else I should look for before taking it apart? And would anyone happen to have a picture of what one of these looks like taken apart and what I should clean/ look for thats broken? Thanks a bunch, if you need anymore info lemme know.

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It's so simple you will see how it works when you pull the housing.
It's got a fork and slides a coupling back and forth.

Get a friend to help you with this.
Put your jeep in park in 2wd, put on the e-brake.
Get under your jeep and pull the vacuum housing off the axle. (some diff fluid may come out)
Have a friend put the jeep into 4wd then back in 2wd and watch to see if the little collar moves. If it works, put it back on - you're fine. If not, you might have/had a line off & you may have gotten dirt into a vacuum line. Take a toothpick or similar tool and see if there are any obstructions. Make sure the 2 vacuum lines that go into the back are secured to the housing (I used zip-ties) as they are prone to coming loose and not letting it build up vacuum.

Another quick fix that I used on mine was to take the housing off and remove the fork from the housing. Then slide the collar over to lock the axle and use a pair of hose clamps on each side of it. With that done you will never have to worry about if the front is connected when you put it in 4wd.

Craig

crasy1_69 said:

Another quick fix that I used on mine was to take the housing off and remove the fork from the housing. Then slide the collar over to lock the axle and use a pair of hose clamps on each side of it. With that done you will never have to worry about if the front is connected when you put it in 4wd.

Craig

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Anyone else ever done this and any ill effects?
blaise :us:

I have already changed 3 of the aluminum forks on my front axle disconnect, seems they would break at the most unopportune time. I finally went to my local dodge dealer and got a cast iron one, and have gone 2 yrs without it breaking.

You can also remove the shift motor, engage the collar over both axleshafts, and install the shift motor upside down. The fork will now hold the collar in the locked position.

Another option...

www.4x4posi-lok.com

Try this...

Get a can of carburettor cleaner, and make sure you have the little swizzle stick.

Remove the shift actuator and take it to a large catchbowl. Working into each vacuum port, spray some carburettor cleaner into the actuator, put your finger over the port, and shake. Put that port at the lowest point you can, and work the fork back and forth until no more cleaner comes out.

Repeat until the cleaner comes out nearly clear, then move to the next port.

I've had these things get crapped up before, and a good cleaning usually does the job. That keeps me going until I get around to doing something else (I like the Posi-Lock idea, but it's a little spendy. I'll do it my way later, with a vernier control cable. Besides, some of these D30 disco fronts are doomed to disappear...)

5-90

Tom_W said:

I have already changed 3 of the aluminum forks on my front axle disconnect, seems they would break at the most unopportune time. I finally went to my local dodge dealer and got a cast iron one, and have gone 2 yrs without it breaking.

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Got a part number or a year and model application for that Dodge fork?

Its a Jeep item.

Did mine when I got the Posi-Loc. I think I asked for a cast iron fork, the dealer had it. Posi also sells them for $50.
Rev

ive seen the cast-iron fork listed in the Quadratec book too.

i just eliminated the 2-peice shaft completely and slapped in a 1-piece shaft to make it non-disco. easy mod but the outer axle housing oil seal is a BEOTCH to replace. ive heard of people running the hose-clamp mod but i'm not comfortable with that. as far as mounting the mechanisn "upside-down and backwards i've never heard that. i ust cut my shift fork off and reinstalled my mechanism as the new cover.

sidriptide said:

ive seen the cast-iron fork listed in the Quadratec book too.

i just eliminated the 2-peice shaft completely and slapped in a 1-piece shaft to make it non-disco. easy mod but the outer axle housing oil seal is a BEOTCH to replace. ive heard of people running the hose-clamp mod but i'm not comfortable with that. as far as mounting the mechanisn "upside-down and backwards i've never heard that. i ust cut my shift fork off and reinstalled my mechanism as the new cover.

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Im guessing you used the d30 axle seal part# front a non-disco axle? Im looking at doing this too, i already picked up the 1 piece shaft..if anyone has a link to a writeup on this that would be great. with a truetrac up front and the 1-piece shaft, should i be expecting any faster tire wear??