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34 minutes ago, Tractorman said:


I know I am posting this a little bit late, but I wanted to clarify some things.  I also apologize for any confusion on my part as to whether you should use the hand-operated vacuum pump or use the engine-driven vacuum pump for troubleshooting vacuum leaks.


I use the hand-operated vacuum pump for troubleshooting vacuum leaks for two reasons.  First, it comes with a vacuum gauge and a release valve which allows you to verify that the circuit being tested is holding a vacuum when you stop pumping.   The second reason is that the hand-operated vacuum pump pumps a very small volume of air so that even a small vacuum leak is easily detected. 


The engine-driven vacuum pump is so powerful that even moderate vacuum leaks will go undetected because of the large volume of air it is capable of pumping.  This is why it is not a good tool for finding smaller leaks.   Also, If you do have small to moderate leaks, the air from the leaks will be continuously pumped into the engine crankcase by the engine-driven vacuum pump.  This air will combine with normal engine blow-by gases and then exit through the crankcase breather..  The higher flow of gases (air mixed with engine blow-by) exiting the crankcase breather will make it appear that your engine has excessive blow-by.   The additional volume from the combined flow may not allow the screen in the crankcase breather to catch all the oil droplets, so you may see an oily mist, as well.. 


In the last 283,000 accumulated miles on my truck, there were two occasions that under certain conditions I noticed an excessive amount of vapor in the air when the engine was idling.  In each of these occasions (using the hand-operated vacuum pump) I found there were moderate vacuum leaks due to failing hoses or connections.  Also, in each of the occasions all of the vacuum operated components (HVAC, CAD, etc.) performed as they should.  So, just because all the vacuum components are working as they should doesn't mean that you don't have vacuum leaks.


It is for the above reasons that I recommend using a hand-operated vacuum pump for troubleshooting vacuum leaks. 


Thank you,

- John

Thank you for the clarification! Makes a little

more sense now! Lol 

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It will be harder in 4wd on dry hard surfaces like pavement or concrete, but hard packed snow and ice, it will be fine as long as your not going so fast that it won't steer where you're pointing the front tires, and steer straight ahead regardless of where your front tires are pointed. Driving too fast for certain road conditions, usually ends in unfavorable results.

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I never noticed my steering any different in 4X4 unless I made onto the pavement and still had it engaged. 


@Tractorman. Your explanation is appreciated and understood. I need to go thru mine a little better.

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When you shift into 4x4, the vacuum switch on the transfer case delivers vacuum (if it has any) to the actuator on the front axle passenger side.  When the axle actuator engages, the switch makes contact and illuminates your 4x4 light on the cluster.  You're not getting 4x4, and you're not getting a light because that actuator is not sliding over.  Either the actuator is shot, the vacuum switch is shot, or your vacuum system has a hole or is plugged somewhere.  I guess your shifter could be a problem too, but I wouldn't know much about that.


I just fixed my 4x4 on a 2001 Cummins Manual.  Here's what I had to do.  First, find the vacuum pump.  Mine was right by the power steering pump.  My vacuum pump only had one line coming from it.  It went directly to the back of the engine compartment basically as close to the steering wheel as you can get, but still be in the engine compartment.  There was a "T" here which had some problems.  My truck does not use vacuum for cruise control, so a line that could have gone down to the servo didn't exist.  If your truck has a servo, you'll need to check that the vacuum lines are good to the servo.  (A vacuum tester is pretty cheap.)  Don't be afraid to pull the lines apart at their connections and attach your vacuum tester.  The plastic parts and rubber hoses are cheap.  Plug any holes that shouldn't be there.  Also, some Dodge's use a vacuum boost to the brake system master cylinder.  Mine didn't.  If yours does, you'll have to check that connection also.  


So anyway, from the "T" that I described, the line turns toward the passenger side of the vehicle.  It has various connections along the way.  Near the passenger side of the vehicle, the vacuum turns and heads into the cab.  This line controls your blowers.  This is why people say that if you don't have vacuum, your blowers will default to "defrost."  My blowers had enough vacuum to work correctly, but my 4x4 didn't.  I never did check the vacuum inside the cab, but I spotted it lately.  Under the driver side dash, toward the stereo, I saw an actuator.  Looked fine and everything powered by vacuum is working great now, so I didn't look any closer and can't describe it in much detail.  You might have to look in there though.  


Back at the original "T" on the drivers side, my vacuum line turned down toward the ground.  This line eventually goes to the 4x4, but don't skip the other stuff, because the whole system has to have vacuum;  I found leaks everywhere on my system.  


So the line stops next at the transfer case (on the top).  At this point it has a vacuum switch.  The switch might be bad.  I replaced mine, but it turns out I probably didn't need to.  Anyway, vacuum is delivered to the switch, then it goes to your actuator inside the passenger side front axle.  There are two lines going from the switch to the axle, and they turn to metal lines along the way.  When you're in 2wd, vacuum is delivered to the passenger side (I think).  When you're in 4wd the vacuum is delivered to the driver's side.  ( Could be the other way around).  There is an actuator device here, that I replaced, and I think it was necessary, but I might be wrong.  See I had taken my truck to the dealership to work on the 4x4 and they couldn't figure it out - It ain't rocket science either.  Well after I fixed all of the vacuum leaks, replaced the switch, and the actuator on the axle, my 4x4 still wasn't working. I was pissed.  After scratching my head for a long time I decided to confirm the vacuum lines on top of the transfer case going into that switch were in the right order.  Sure enough, they had been changed around so that vacuum wasn't being delivered right at all.  So be careful to make sure all of those lines are right. Who knows, I might have messed them up, but I don't think I changed them around at all.  I think the dealership did.  Anyway, they didn't fix my 4x4, I did, and I'm better off for it.  The harness that goes on the switch is junk too, and my parts houses couldn't find it.  I ended up putting a zip tie around the base of it, and that helped.   Good luck!





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On 12/31/2017 at 10:41 PM, JP907ATB said:

My actuator down on axel froze up, instead of ordering a new vacuum actuator, I ordered the posi lock cable from summit racing. It replaces the vacuum  actuator with a mechanical cable. It’s much more reliable in my opinion, it’s not as user friendly as i have to put it in neutral or reverse even to get it to disengage. Also have to be rolling a little to get the collar to slip over the passenger axel when you first engage, but it works for me.


I will vouch for the 4x4 posi-lok as well. I no longer worry about my actuator failing on my 98.5 at the worst time and the 2WD low is great for backing trailers.


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