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Old 03-29-2009, 06:01 PM
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Everything You Wanted To Know About The IWE System...And Then Some

After my recent experiences with the complete IWE system i decided to write up a description of the system and troubleshooting. Hope this helps out some people!

Maybe this can become a sticky!

When the system is working correctly, vacuum is placed on the system unlocking the hubs while the truck is running. When shifting to 4WD vacuum is relaesed, locking in the hubs. A vacuum leak at any part of the system can cause failure.

When the engine is started and running, vacuum is exerted on the entire system, unlocking the IWE actuators. When the engine is turned off or 4WD is engaged (either by floor shifter of dial selector) vacuum is released by the IWE solenoid to the actuators at the wheels. So vacuum to the actuators at the wheel unlocks the hubs for 2WD and release of vacuum by the solenoid locks them for 4WD.

When the vacuum builds when the engine is started, the vacuum from the intake via a vacuum line exerts vacuum on the entire IWE system all the way to the actuators. The first check valve locks the vacuum at the highest vacuum that is exerted from the engine from that check valve down. The vacuum box now holds that highest vacuum exerted also. The second check valve located right before the IWE solenoid holds the highest vacuum to the actuators from what has been exerted from the engine.

As you start to understand the vacuum system and series of check valves, you will see that the vacuum box that is located between the two check valves does in fact act as a reserve. When you engage the 4WD, vacuum is released by the solenoid and locks the line from draining back. This process allows the lines and vacuum box between the two check valves to hold the current highest vacuum even though the engine vacuum is constantly changing and the vacuum from the second check valve to the actuators have been lost. When 4WD is disengaged, the solenoid is opened back up, the high vacuum from the reserve from the vacuum box is then used to then exert vacuum on the lines to the actuators unlocking the actuators no matter what the vacuum from the engine is. When this little bit of vacuum is lost in the reserve it is then rebuilt from the engine when vacuum is increased from the intake.

After saying all of that and you think about what the manual says about turning the 4WD on and off, you notice that you are supposed to activate and deactivate the 4WD while under a certain speed and while not accelerating. This ensures two things, high speed engageing and disengaging of the gears in the hubs which can cause mechanical damage does not happen. It also allows a quick window of no load and low RPMs from the engine, hence high vacuum from the engine, that will quickly replenish the high vacuum to the entire system and "locks" that vacuum between the two check valves and reserve box for the reserve, as well as from the second check valve to the actuators.

This, when working correctly without any leaks always ensures a high enough vacuum to keep the acutuators unlocked when your in 2WD, or unlocking quickly when shifting from 4WD to 2WD. A leak in one of the lines,the reserve box, or an actuator, or a faulty check valve will allow a leak down in vacumm somewhere in the system that will allow the actuators to possible try to engage or close to it when not needed while driving, giving you the grinding or whinning noise of the gears of the actuators trying to mesh together at highway speeds.

To test the vaccum system, get a good vacuum pump with a guage on it, about $60 (or cheaper) at alot of parts stores.

-If when you try to shift into 4WD and it will not engage, most likely your solenoid is not working and releasing the vacuum to the actuators and engaging the hubs. Replace the solenoid. This might happen because of the early design of the IWE solenoid with lets water run off the cowl right down on top of the solenoid possible shorting it out. The new style solenoids have a rain cover on them to prevent this. This is all being said as long as you know your shift motor on the side of the tranfer case is working properly.

-If your in 4WD and it will not shift out, the solenoid is not opening back up to let vacuum release the actuators. Replace the solenoid. Again if the shift motor is working.

-If you hear a grinding or whining of gears at certain speeds or loads you probably have leak in your vacuum system somewhere and your vaccum is dropping to or below the 5 lbs of vacuum needed to keep the actuators unlocked. Check the following:

One wheel at a time unplug the double vacuum hoses from the actuators at the wheel located behind the steering knuckle. Put your vacuum pump on the big hose fitting and pump up the pump. If it is woking correctly you will be able to build up vacuum and it will hold. A vacuum loss of 1 lb over 1 minute is acceptable. If you can not build vacuum or is leaks down very fast, the seals on the actuator are shot and the actuator needs to be replaced.

Next check your lines from the solenoid to the actuators at the wheel. Pull the double vacuum line off the solenoid. Pull the double vacuum line off of both actuators at the wheels. Plug the hoses at the wheels. (you only need to plug the big hose a the wheel, and make sure you have a good plug that seals 100%) At the double hose that you took off the solenoid, trace the lines, you want the line that goes down to the wheels, not the one that goes to the intake. Take your pump and connect it to the line end from the solenoid that goes to the wheels. Pump the pump up and see if the vacuum on the guage holds. If it does not and leaks down, you have a leak in your lines between the solenoid and the actuators. Check the lines very thoroghly from the solenoid to the wheels, its hard to get to some of the lines, but they all need checked, look for cracks or breaks. Replace the lines with factory ones from ford or make your own, like i did with bulk vacuum hose and some fittings. If the vacuum you create with the pump holds your lines are good, but still look them over for obvious faults.

Then you will want to check the vacuum reserve box that is mounted behind the battery on the battery tray. You will have to remove the battery and battery tray to access it. Once removed and the vacuum line disconnected from it, connect your vacuum pump to the fitting on the box and pump up the pump, if it pumps up with vacuum and holds it is ok. I fit doesnt build vacuum from the pump or leaks down, the box is leaking and needs to be replaced (ford only part).

Now plug the line you removed from the vacuum box, this line runs to the intake with a "T" in it. The line from the "T" goes to the solenoid. Plug the end that goes to the solenoid also. Unplug the same line at the check valve that is close to the intake. Connect your pump to that end of the line and pump up the pump. If it pumps up vacuum and holds, that line is ok, if it wont pump up or leaks down then there is a leak in that line, replace, fix, or make a new line.

There are two small check valves in the line coming off the intake. One close to the intake and one in the same line close to the solenoid. Pull those check valves off and check them. An easy way to check them is to blow (with your mouth, not compressed air, this will blow them out, i know) You should be able to blow through one end and not the other at all. Or you can check it with the pump. One side of the valve will say "VAC" connect your pump to that end and pump it up. It should pump and hold without any leak down. If it does not then replace it. If it holds its good. If one or both of these fail, the high constant vacuum will not be held correctly in the system and while driving, the vacuum could drop too low and try to engage the actuators.

If all of this checks out ok check the vacuum straight from the engine. From the line coming off the engine connect your pump to the line and turn on the truck. Watch what poundage of vacuum shows up on your guage (you will not have to pump it up) should be anywhere from about 17 to 22. Ive read that 20-22 is normal but mine likes to hover around 18-19 at idle. If this reading is too low you might have another vacuum leak somewhere else on the engine.

Remember the 4WD engagement or lack there of is considering that you shift motor on the transfer case is working properly.

If you suspect that your system is malfuncting and you are not able to test it right away or want to drive and not damage anything, disconnect the line coming off the intake at the check valve and plug both ends of the line. This will not allow any vacuum to reach the system and leave your hubs locked in all the time. This is fine and wont cause any damage as long as the hubs lock correctly. The half shafts and front driveshaft with the front differential will turn but the 4WD will not be engaged. You might notice a drop in MPG, but it is now safe to drive.

I hope that my investigation into the system and explination helps alot of people understand the system and help troubleshoot it. Anybody feel free to add to this, but i think i covered it pretty deeply.

This is a rough layout of the IWE vacum line system. From what i can gather and understand from the vacuum system for IWEs, there are two check valves and when working correctly and without any leaks in the vacuum system they hold the vacuum to the IWEs at a constant vacuum even thoguh the vacuum will change at the intake with engine load and RPMs.

Click the image to open in full size.
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Old 03-29-2009, 10:26 PM
AAK625 AAK625 is offline
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Wow. I don't know what half that stuff is, but damn nice write up! If you have a camera, you may want to snap some photos too.
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Old 03-30-2009, 07:21 AM
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Ill try to get some pics, but its hard to get to some of the stuff. If you just look at the engine bay on the passenger side and look at my diagram you will begin to see what each part is.
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Old 03-30-2009, 12:02 PM
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Great Job! I have two questions. 1. I can't remember what IWE stands for. 2. It sounds like there is one line coming from the "T" at the engine to the vacuum box and another line going to the IWE solenoid. I'm guessing that second line is what activates that solenoid. Correct?
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Old 03-30-2009, 12:15 PM
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IWE stands for "Integrated Wheel Ends". And yes the line coming off the engine T's off and one end goes to the vacuum box and the other feeds the solenoid. It doesnt activate the solenoid it just feeds the solenoid with the vacuum to supply it down to the actuators at the wheels.
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Old 03-30-2009, 05:46 PM
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I take it you got your pulling problem solved?


Very nice write up!

Rep points to you!!
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Old 03-30-2009, 05:52 PM
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Holy cow! That's a thorough write-up lol!

x2 sticky or tech article

Rep'd you as well xjcamaro89

Good job.
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Old 03-30-2009, 08:16 PM
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Yes when i tested the system on saturday the truck was much better, pulling gone and ride is much smoother and truck performance is much better, all of those cleared up because of no more rotating mass of the entire front driveline and the truck having to "push" the front driveline during use. I currently still have the vacuum lines pulled and plugged until tommorow because i blew up the vacuum box while using compressed air blowing out the vacuum lines and the box wont be in until tommorow. Also when i was testing the system (with a epoxyed together vacuum box that was still a little leaky) i notice still a small leak down while cruising on the highway, i later found that my vacuum guage, that was connected to the system for testing while driving, was laeking and causing the slow leak down. I got a new vacuum guage and after i get the new box tommorow and put it in and hook everything back up i will take it for a test drive and everything should be good to go tommorow. I cant wait cause i think the actuator was shot when i got the truck almost a year ago and i just found it last week. So after the improvement i felt from the truck when testing, its going to feel like a completely different truck, and my gas mileage should go up too!

Thank you for the rep points and i hope this helps alot of people cause i did run into the problem while searching for answers. I couldnt really find all the answers i was looking for and they were pretty scattered. People had little problems here and there with the system, so i took what i figured out and some that i read from other posts and put them all together in one place for everyone.
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Old 03-30-2009, 09:33 PM
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That was an impressive write up! I just spent 10min reading that but I'm glad I did.
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Old 03-31-2009, 07:12 AM
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Thank you!
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Old 03-31-2009, 06:31 PM
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Ok, update! I put the new vacuum box on and hooked everything back up and took it for a 50+ mile drive, and success! Its working the way its supposed to. I did notice a very minute leak down on my guage while cruising on the highway, i thought this was going to be normal, but then i thought about the check valves again. The leak down never dropped below about 17 on the guage so it wasnt enough to do anything. After i got home i tested my vacuum pump just to make sure (cause my last one took a dump while testing and gave me the same results) and sure enough the connection from the vacuum pump line to my test line i installed inline with the lines going to the actuators was leaking. I put some sealant on the connector (some sort of sealant that came with the pump) and bench tested the pump and test line again and it held fine. So there is a lesson to you guys, test your testing equipment also. Just for safe measure i retested the actuators and lines to make sure they were all ok too and they were, so everything is now working properly from what i can see. Im so excited the truck felt completely different now that everything up front wasnt turning as well. Much Better!
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Old 04-11-2009, 10:16 AM
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Hi XJ
THANK YOU!!For this explanation.I have an understanding of the system now.I thought the transfer case was acting up causing the grinding noise.I do want to have the system looked at though&never did brakes b4.If I lived closer to you,I would have you look at it&of course,pay you.
I drove the truck home from work last night&didnt fiddle with the 4wd at all&I heard nothing wrong at all.Guess I will keep the truck in 2wd&not fool with it.What works for me is when i go from 4wd to 2wd,the minute I shift to 2wd going about 30MPH,I slow down to a crawl until I hear a gentle clunk then I know Im fine.I know eventually I have to get the system looked at but for now I just wont shift&just keep it in 2wd.
We had a very cold winter here&drove in snow.Isnt there anything that can be done to protect this system from the elements?My truck is rather young,45k miles on her,just baffled at this whole thing.
I was playing in mud last month&got stuck&tried rocking the truck out going 4wd then reverse.Wondering if I messed anything up?Guess I did.Another pickup with a winch got me out.....Pete
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Old 04-11-2009, 11:17 AM
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You vacuum system could have injested water or mud into the IWEs or vacuum lines and that in turn some how wont let the vacuum release at the hubs completely and letting the hubs lock in.
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Old 04-11-2009, 11:40 AM
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could I pull out the lines from the wheel&Check?You think they would make it so no foreigh material would get in&do the lines just get put back in place?
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Old 04-11-2009, 11:45 AM
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Yes there is just a metal tube sticking off the IWE actuator rings at the wheel. the hoses slide off and back on.
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Old 04-11-2009, 11:45 AM
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