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4x4 won’t work! Help

Marcus2000monster
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Dieselfuture

Dieselfuture

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Have you checked by cad if you got vacuum, and you can put a hose on actuator and suck vacuum on each fitting and it will engage and disengage. If all checks out there, then there is something by the transfer case that I never messed with myself but I know it's there. I wanted to eliminate as much as I could with all that vacuum stuff that's why I went with a cable instead, plus having a 2low is nice for backing up hill with a trailer, which can be done other ways. I just wanted to try posilock, and my actuator was on the way out so I was almost half way on the cost just replacing it. 

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Marcus2000monster

Marcus2000monster

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1 hour ago, Dieselfuture said:

Have you checked by cad if you got vacuum, and you can put a hose on actuator and suck vacuum on each fitting and it will engage and disengage. If all checks out there, then there is something by the transfer case that I never messed with myself but I know it's there. I wanted to eliminate as much as I could with all that vacuum stuff that's why I went with a cable instead, plus having a 2low is nice for backing up hill with a trailer, which can be done other ways. I just wanted to try posilock, and my actuator was on the way out so I was almost half way on the cost just replacing it. 

I’m in the middle of doing so. Going to bed shortly I will continue tomorrow! Sure hope I can fix cuase it’s dumping snow right now! :thumb1:

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Marcus2000monster

Marcus2000monster

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On 12/29/2017 at 8:32 PM, Dieselfuture said:

Have you checked by cad if you got vacuum, and you can put a hose on actuator and suck vacuum on each fitting and it will engage and disengage. If all checks out there, then there is something by the transfer case that I never messed with myself but I know it's there. I wanted to eliminate as much as I could with all that vacuum stuff that's why I went with a cable instead, plus having a 2low is nice for backing up hill with a trailer, which can be done other ways. I just wanted to try posilock, and my actuator was on the way out so I was almost half way on the cost just replacing it. 

I have not tested this yet I need to do so. I ended up going to town yesterday so didn’t get everything done I wanted to. Maybe this afternoon I can try this. 

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Marcus2000monster

Marcus2000monster

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11 minutes ago, Mopar1973Man said:

Like on mt 1996 Dodge Ram 1500 the vacuum motor got struck by something and tweaked the shaft causing it to hang up and stick randomly. Full replacement of the vacuum motor isn't hard but it would sure take care of any vacuum issues.

I am willing to do that if the motor is bad but I don’t want to throw parts at her. I also need to finish checking for vacuum at the switch on the transfer case. 

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Marcus2000monster

Marcus2000monster

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On 12/29/2017 at 10:48 AM, Tractorman said:

A hand operated vacuum test pump is a good investment, is not that expensive, and will allow you to accurately diagnose vacuum related problems. 

 

For example, the CAD unit can easily be tested.  Place the transmission into a gear and select 4-high or 4-low with the transfer case.  Jack up the right front wheel and disconnect the vacuum lines at the CAD unit on the axle.  Connect the vacuum pump to one port of the CAD unit; leave the other port vented to atmosphere.   Operate the vacuum pump and hand rotate the right wheel to ensure engagement or release of the CAD.  Swap connections and test again.  Assuming that vacuum held on each test, one test should allow the wheel to rotate freely, the other test should lock the wheel in place which means that the CAD is mechanically doing its job.  Using the vacuum pump you can continue with testing of all vacuum lines until you find the source of the problem.

 

If both tests pass and the 4WD light does not come on, then you have a bulb failure, an electrical wiring problem, or a CAD switch contact failure.

 

If the right wheel spins freely during both tests, then you have a CAD failure.

 

Vacuum leaks on these trucks are commonly overlooked until something fails.  The vacuum pump is very powerful and vacuum leaks can go undetected until they become large.  Remember, all air from these leaks pass through the vacuum pump, into the engine crankcase, and then out the breather vent.  You do not need this additional air flow out the breather vent!  This issue alone is reason to invest in a hand operated vacuum test pump.

 

- John

In this test to run the vacuum pump I just need to run the engine right?

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Marcus2000monster

Marcus2000monster

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Just now, dripley said:

I dont see why not unless I am missing something. Using the hand held pump would eliminate the CAD as the problem if the engine pump want make it engage. 

We’re gonna give If a shot!

I must be really dumb! Of course this test is going to fail because obviously the truck isn’t going into 4 wheel drive! :doh:

Grumph.... 

Ok so I started he truck and took the black and red vac lines off the cad unit and felt either very very small amount of vacuum or none. Put t case in 4 and got the same. 

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Mopar1973Man

Mopar1973Man

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So basically you have to back track now and figure out where the vacuum is going. Start at the vacuum pump and work your way forward looking at all the tubing. I've been known to pull the tubing and bend it arch and see if the tubing breaks or splits open. Funny how a plastic tube will look fine arch it and it will either split open more or break.

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Marcus2000monster

Marcus2000monster

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3 minutes ago, Mopar1973Man said:

So basically you have to back track now and figure out where the vacuum is going. Start at the vacuum pump and work your way forward looking at all the tubing. I've been known to pull the tubing and bend it arch and see if the tubing breaks or splits open. Funny how a plastic tube will look fine arch it and it will either split open more or break.

I do have a leak somewhere. My vents do not switch. It is stuck on defrost. Which line supply’s that?

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Mopar1973Man

Mopar1973Man

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Basically, there is only one line from the vacuum pump up to the cowl then it tee's off for the CAD unit then continues across to the passenger side for the HVAC controls. You'll see the vacuum line running in with the A/C tubing. You've now confirmed the leak for sure with HVAC controls stuck in DEF mode is sign of a vacuum failure. So I would leave the truck idling start at the vacuum pump and keep working away from the source of vacuum replacing anything you find damaged or rotten. The rubber tubing end are known to split too.

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Marcus2000monster

Marcus2000monster

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11 minutes ago, Mopar1973Man said:

Basically, there is only one line from the vacuum pump up to the cowl then it tee's off for the CAD unit then continues across to the passenger side for the HVAC controls. You'll see the vacuum line running in with the A/C tubing. You've now confirmed the leak for sure with HVAC controls stuck in DEF mode is sign of a vacuum failure. So I would leave the truck idling start at the vacuum pump and keep working away from the source of vacuum replacing anything you find damaged or rotten. The rubber tubing end are known to split too.

K guys please don’t laugh at me because I feel really stupid! I went and popped the hood and looked down and boom there was a vacuum line laying right there unhooked from the connecter. Started truck and shifted straight into 4x4! :doh::doh::mad:

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Mopar1973Man

Mopar1973Man

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Just now, Marcus2000monster said:

Thanks! I’m glad it was free lol! Sorry for wasting your time! :wink:

 

Never wasted my time... That what I'm here for is try to help others out. 

 

As for having the line come apart like that I've been known to be working on y truck move the line out of my way and end up forgetting to hook it back up. 

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