My 4 wd  is not engaging. I have tried searching with no luck. Must not be entering the right words. The dash light does not come on. My mind has drawn a complete blank on what to look for! I know it is something simple! Thanks

Update: I have vacuum at the tranny, but no vacuum  at the CAD. There must be some type of vacuum switch in the tranny that is preventing the vacuum to go to the CAD. There is a vacuum connector that connects the hose from the fire wall (gray), to the cad (red and black), and a green one. I don't know where the green one goes to. Is my next step tranny removal to fix the problem?

nomore,

 

here is a picture i posted in another thread.  Yes the there is a three way switch on the transfer case.  It senses the location of your transfer case lever.  It provides vacuum to the red or the black based on if you have selected a 4wd mode or not.  If it is original, red is 2wd and black is 4wd.  (red pulls the CAD vacuum motor to disconnect the coupling.   Black pulls the vacuum motor to engage the axle coupling. 

 

Here is a video of a guy checking his out.   I did not watch it all but it seems ok.  he never shows the actual switch.  that goes bad rarely.  you can easily disconnect the vacuum plug from the switch from below and test each of the vacuum tubes.

 

Our switch, unlike the GM verson has 4 tubes connected.  (GM only uses 3)  our 4 are  White=vacuum source, Green= Vent to atmosphere (to change directions of the vacuum motor, you must exhaust (let the side under vacuum return to atmospheric pressure) , Red = 2wd by disconnecting the axle coupling if the vacuum motor is actuated in that direction, Black = 4wd by moving the vacuum motor and coupling to engaged the shafts.

 

Haggar,

 

Thanks for the video. My problem must be the switch. I know I have vacuum to the switch. Nothing past that.  The front drive shaft turns. I will look into the switch.

This may help as well:

 

 

Went to NAPA to try to get a vacuum switch for a 241 transfer case. Their books only listed a 231. If I am reading the parts look up tool correctly, they use the same one. Any one have any experience in them being the same?

I would guess something like that would be the same. But not positive.  I ended up getting posi lock for mine, so far it worked good.

 

I replaced my vacuum switch and still do not have vacuum at the CAD. Does anyone know how the vacuum switch is activated?

Do you have vacuum at fire wall? Where it splits 

Yes, I have vacuum at the connector that attaches to the transfer case vacuum switch. It is brand new. Just can't get vacuum past the switch!

Is there a chance to plug it in backwards, if you got the vacuum to the switch then whatever controls it would be the next step

No, it has guides on it that match the switch and the plug. I thought of that myself.

Probably just a bad line then going to the axle

Nomore,

 

IIRC, there is a detent ball at the bottom of the new switch you got.  That detent ball rides on a shaft in the TC.  The shaft has flats and round to actuate it when it is in the proper position.  (I cant remember if it is the mode shaft or the range, but think it is the mode.)

 

Take the vacuum switch back out and manually operate it with your hand. (push the little ball in) and see if it directs the vacuum properly. 

 

I found another drawing that might help you with which vacuum line goes where  (note, I have not verified this, but seems like how I remember it.)    Looking at the switch from the "top" (vacuum side) down.  The vent goes between the arrows.

 

I just found another picture from a jeep forum (http://www.wranglerforum.com/f218/vacuum-issue-in-4wd-system-with-light-1677905.html)

 

notice for his he has reversed the vacuum and vent ports.  but that does not matter as long as you swap the "outputs"  .

 

Hope this helps

Thanks Haggar,

That is what I was planning to do on Sunday. Live under the truck till I fix it!

 

After replacing the vacuum line connectors, went thru and made sure I didn't cross the red and black lines somewhere. Didn't. Checked for vacuum at the switch, good. Checked vacuum at the first connection at the tranny cross member. Good. Checked at the CAD connection. Red good, black bad. Pulled the metal tubes from the frame, looked to see if it was crushed. Nope. Tried blowing thru it. Nothing. Applied air pressure to clean it out. Connected everything back up, put it into 4wd High and all of the wheels rotate. FIXED! The dash indicator doesn't come on, I can live with that. That must be the indicator switch. I was surprised that the metal tube had actually clogged. Thanks for the help everyone.

 

 

 

Glad to hear you got it figured out.

 

L8tr

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