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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

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 If transfer case shifts and front shat locks, could be a cad. Something I just fixed on mine. 

 

It's more likely something to do with cad as the light for dash gets tripped when pin that holds shifting fork moves, so like stated above ether vacuum leak, or maybe vacuum pump. Is your hvac function properly, or stock on defrost. Either way check for vacuum leaks first, old vacuum lines get mushy and crak.

Edited by Dieselfuture
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Most likely the vacuum lines for the CAD unit. Next would be the CAD unit itself needs rebuilding. The vacuum motor can get leaks or the shift fork shoes might be worn out. I'm glad I don't have a CAD unit on the 2002. The 1996 with the CAD has left me stuck a few times because the CAD unit didn't lock in like it should.

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19 minutes ago, gassernomore said:

Why no lite on the dash?

Just edited my post

You can see in pictures of this post that fork pin and sensor the trips 4x4 light

https://mopar1973man.com/topic/12424-front-axle-cad-vacuum-actuator-to-manual-posi-lock/

@Mopar1973Man so when you don't have a cad, does your front drive shaft always spin then?

@Mopar1973Man

Edited by Dieselfuture

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1 hour ago, Mopar1973Man said:

 

So what? At least my 4WD works all the time on the 2002 where the 1996 might not work when you really need it. 

No, I was just curious if that is what it does, in my mind I always thought why spin extra parts when you don't need to. And I'm a big fan of lock out hubs, but as expensive as that conversion is don't see it happening any time soon. I can understand why doge did it, save money and convince to driver, as most people that buy new vehicles want convince over durability as they're going to trade it in anyway. I thought cad was a dumb idea but in my mind better then always locked. I might be wrong as usual., lol.

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45 minutes ago, Dieselfuture said:

No, I was just curious if that is what it does, in my mind I always thought why spin extra parts when you don't need to.

 

Extra spinning parts... LOL. At least they work 1005 of the time where my 1996 Dodge with CAD without constant axle has left me stuck because of engagement issues. 

 

52 minutes ago, Dieselfuture said:

I'm a big fan of lock out hubs, but as expensive as that conversion is don't see it happening any time soon.

 

Just like @MUDDY trying to convince me of doing the conversion on my truck during the bearing change out. Yeah, so you got manual hubs, standard cone bearings, etc. Still in all, I don't want the headache of manually locking hubs and messing with packing bearings. 150k-180k miles on a set of bearings is not bad. That is one job I hate doing on the RV breaking down the axles one at a time using an entire can of grease on repacking all 8 bearings. 

 

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Nice thing about having the CAD is easy 2wd Low.  :woot: Then again there are still workarounds without going for manual locking hubs.

 

Mike, if you really despise the CAD in the 96, just disable it.  The collar will stay locked and it will be like it was no longer there.  I'm half tempted to do this, but haven't had any problems with the 4x4 of yet that would warrant it.  And like said, I don't really mind my front shaft not spinning all the time.

Edited by Cowboy

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8 hours ago, Cowboy said:

Mike, if you really despise the CAD in the 96, just disable it.

 

Mom had the same system in her old Chevy S10 pickup years ago. Many times that vacuum line dropped off and the front axle never locked. Like my old 94 Check pickup (Fire truck) was an electric locking and I've had the solenoid burnout on a fire call and got me stuck in the snow.

 

2WD LO I never needed such a thing. Even with all the trailer work I do I've never need a 2WD LO.

 

As for the CAD system. I'm going to leave it alone being this is my fail back truck that has it. I've already rebuilt the entire setup and I know it works for now. 

Edited by Mopar1973Man

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Well yeah, no one ever needs 2wd low.  A nice-to-have... very much so.  

 

Either way it's your rig and is up to you.  You seemed to be extraordinarily passionate about your non-CAD prefferences, so I thought I'd throw the idea out there.

 

gassernomore, best way I've found to find a vacuum leak on the 4x4 system is to just throw it in 4x4, grab the black line off the CAD actuator on the axle, and blow into it... hahaha  you'll hear it leaking from you leak.

 

Edited by Cowboy

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Isn't there an aftermarket cable you can install for manual control that gets away from the vacuum line problems?

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Update: Finally had a day off to work on the truck. Replaced all of the vacuum connectors that I could find for the vacuum system. Now , my a/c system is blowing from the defrost area only.

 

I am thinking I lost my vacuum pump. I don't know how much vacuum it takes to energize the cad or the a/c controls. Not sure if it is possible to energize  the system but, I tried sucking on the vacuum lines and nothing happened.

 

Any thoughts?

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The vacuum line that goes thru the fire wall for the ac on mine got brittle and broke. Had to cut part of it off and reconnect it. Do you still not have 4wd?

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Do you have a pump type brake bleeder?  You could probably use that to test the system.  I am assuming your hvac wasn't working while the motor was running.  It sounds like you loosened up another line when you were working on it.

 

L8tr

D

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Silver moose is dead on.  Use a hand held vacuum tool like this https://www.harborfreight.com/Brake-Bleeder-and-Vacuum-Pump-Kit-69328.html

 

connect it where the lines connect to your vacuum pump now.  pump the handle, and if it never pulls a vacuum, there is a line loose somewhere.  Keep pumping and have someone listen around for where the air is leaking from.  (they should easily hear the hissing, unless it is a huge hole)  after you have fixed your leak  you should be able to keep pumping the handle and have your HVAC vents move (no, truck need not be on)  and your 4wd actuator should try to move. (no the light won't come on with the key off, but the valve is mechanical and connected to the Transfer case near the shifter)

 

To check your vacuum pump on the motor, connect this tool directly to the vacuum pump.  start the truck and read the gauge.  (the vacuum pump on the truck, if working and no leak (there should be no leak you are connected directly to it) you will see how much vacuum your pump on the truck is pulling. 

 

Hope this helps!

 

Hag

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Thanks guys. When I try to suck the air from the lines, I can't move any more air from the lines. So, I believe I have no leaks. That is why I am believing the pump is out. I will look for a vacuum pump.

 

 

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4 minutes ago, gassernomore said:

Thanks guys. When I try to suck the air from the lines, I can't move any more air from the lines. So, I believe I have no leaks. That is why I am believing the pump is out. I will look for a vacuum pump.

 

 

https://www.genosgarage.com/product/GG10FV/engine-rebuild-kits-2

https://www.genosgarage.com/product/gould-vprk-9602/engine-rebuild-kits-2

 

I would look on ebay for the reseal kit though. I think you can get them for around 25ish.

 

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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?

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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.

 

Vacuum Lines.jpg

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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.

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