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  #1  
Old 03-17-2010, 07:37 PM
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permanent fix for 4wd vacuum IWE

Hey all, I was following a thread on the IWE problems associated with leaking or otherwise malfunctioning vacuum system, and I had a question about a permanent fix.

Has anyone tried simply disabling the vacuum system entirely? You can block or plug the vacuum line at each IWE, which will permanently lock them.

So hear me out...
By locking the front hubs permanently you will cause them to always spin the front axles, and turn the front differential. However, unless the truck is actually in 4wd mode the front diff gets no power supplied to it, because the front driveshaft is not engaged by the transfer case. So, you will get increased drag, which may adversely affect MPG, and there is a slight possibility that you will lose some performance due to drag on the front wheels. However, I can't see that it would be that bad. Certainly it wouldn't be any worse that the pre 2004 models with 4wd, right? Because that is essentially how their systems operate.

My understanding is that the IWE are only there to decrease drag on the front drive train when in 2wd to increase fuel economy.

From reading the document on "principles of operation" for the Ford 4wd system, it seems to me that two things happen when switching to 4wd. First the transfer case shifts over to engage the front drive axle, while it does this it also uses a clutch to make the front drive axle match the speed of the rear drive axle. If the axle is already turning because the front hubs are locked, then this should be unchanged from standard.
Then it locks the front hubs using the IWE. Since they are already locked, this step is unnecessary. There would be no need to change any components, the vacuum system would still go through the steps to lock the IWE, just nothing would happen.

So what you would be left with is a system that only has the transfer case and its components as moving parts when switching to 4wd. No worries about water in the system, no problems with vacuum leaks.

It just seems to me the IWE system is superfluous, it serves no purpose other than to make the system more complex and unreliable. All for a gain of maybe 1-2 mpg.

So, concerns that I have are driveline wear, and increased drag. Drag isnt the biggest issue, I could live with slightly lower MPG. But if it caused significant loss of performance, then that could be an issue. Driveline wear is a biggy. Potentially you could have problems with the transfer case if the order of doing things is messed with. It is supposed to get the front shaft sped up, engaged, get the axles spinning, and THEN engage the hubs. So I don't know if this would cause problems or not.

So this is my idea. Anyone tried this, on purpose or by accident? Anyone who has not tried it but has some technical knowledge want to chime in?

Cheers!
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  #2  
Old 03-17-2010, 08:13 PM
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yea but the pre- 2004 models like mine, spin the axle shafts not the drive shaft and front end which is what causes the most drag and noise
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  #3  
Old 03-17-2010, 08:46 PM
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Im not going to say it will work but...i do know that AWD F150s such as the Limited and Harley do not have an IWE solinoid. They do have IWEs but no vacuum lines run to them they are just capped off and permanently locked. The front driveshaft always spins on the AWD models and power to the front driveshaft is varied by a duty cycled magnetic clutch.

However without an AWD tranfercase you may do more damage then good. The IWE system works great why would you want to change it?
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  #4  
Old 03-17-2010, 09:45 PM
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@ Steven's - So the pre 04 system doesn't turn the diff or the drive shaft when not in 4wd? I thought there was a "sleeve' that was activated by the 4wd switch that slipped over the driveshaft to connect it with the transfer case. Is it actually something in the diff that engage when 4wd is turned on?
@ Paralyzer - Interesting about the AWD. So at least the noise and drag can't be that bad, otherwise the they would have come up with another solution. My concern is also with the transfer case not being up to the task. The problem that I can see is that the driveshaft will be the part that absorbs the torque shock from the shift into 4wd, rather than the IWEs. I guess this could be minimized by only going to 4wd at low speeds....
The reason I would consider it is the inherent unreliability these IWEs seem to have. I think it is a fantastic design in some ways, but really stupid in others. A vacuum system in a 4wd truck that is so sensitive to dirt and moisture makes no sense to me. What happens when you get into water that is deeper than you expected and submerge an hub? The IWEs not being water proof is an extremely poor design in my opinion.
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  #5  
Old 03-18-2010, 12:03 AM
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I have heard of some people removing/plugging the vacuum lines to essentially have "live axles" up front. I was considering looking into AWD expedition front wheel bearing/hub units as they are always engaged I believe until I realized I could achieve the same result by removing the vacuum lines.
I haven't tried this in mine, but I have heard that some people (not first hand info) get a significant amount of extra noise from the transfer case when doing this. That would surprise me if that were the case, unless something in the transfer case is significantly different than most. 01+ Rangers, 95-01 Explorers, 01-05 Sport Tracs all had live axles up front with the front drivetrain turning all the time. MPG loss was minimal.
I also had a 98 Ranger with vacuum hubs, which also used an electromagnetic clutch to bring the front driveline up to speed before engaging the hubs. A lot of people modified the hubs to stay locked, and eventually a company offered manual hubs and I used them, left them locked all the time.

I did unplug the solenoid (electrical plug, not vacuum) on the firewall of the F150 one day, which made the hubs stay locked with the truck running. But when I turned the 4x4 switch the light came on for a second, then turned off and nothing happened.

Unplug the vacuum lines and let us know how it works.
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  #6  
Old 03-18-2010, 12:07 AM
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Quote:
Originally Posted by wildvodka View Post
@ Paralyzer - Interesting about the AWD. So at least the noise and drag can't be that bad, otherwise the they would have come up with another solution. My concern is also with the transfer case not being up to the task. The problem that I can see is that the driveshaft will be the part that absorbs the torque shock from the shift into 4wd, rather than the IWEs. I guess this could be minimized by only going to 4wd at low speeds....
The integrated wheel ends do not take a load when shifting into 4x4. There is an electromagnetic clutch in the transfer case that brings the driveline up to speed, then engages the transfer case, THEN the hubs lock after everything is equal. The only time the IWE is taking a load shock is if you are spinning the tires while engaging 4x4. If the front driveline is spinning all the time (live axles) you should be able to engage 4x4 at any speed. That's how it worked on my ranger with manual hubs, and my sport trac with live axles.
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  #7  
Old 03-18-2010, 01:10 AM
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Thumbs up

Removing the hoses and capping the ports and lines to prevent ingestion of water, etc .... wil not hurt anything except gas mileage and kill some small bit of acceleration, as you are introducing drag.

You will cause the IWEs to engage and stay engaged which will then cause the front axles shafts and front drive shaft to turn at road speed. The 2 hi will still be 2 wd, the 4 hi and 4 lo willl still engage and dis engage, you just won't hear the IWE's engage ... or wait for same. If run on hard pavement, you will still have to maybe stop and back up to relieve loading to get out of 4 wd into 2 wd.

You will wear the front CV joints and shaft universals and bearings more, they may still outlast the truck?

As pointed out, the front end will see life just like the front end of a Harley or Limited. There's no added stress on a part time transfer case, the connection from transfer case to front shaft is open as long as the motror swithed it back last time. In 4 wd the transfer case would see life same as stock.

The full time transfer case just has an added "differential" of sorts between the front and rear drive shafts to allow for thier turning different speeds which happens because of different tire loading / air pressures / turning radius (front end has to travel further around every turn).

What I'ld be interested in doing is come up with a way to easily use the 4 Lo position without engaging the IWEs. For those times where you might want to pull a heavy load slowly up a paved steeply graded driveway or hill (like going up Grandfather Mountain). Maybe a camper, maybe a trailer loaded with firewood, where you would enjoy taking advantage of the lower ratio in the transfer case so to go up at low throttle while not beating the hell out of the transmission.

I can do this with my '77, it has manual hubs. I'ld be pleased to have manual hubs on my '07 ... I know enough to not be running it full throttle in low.

Any ideas out there?

I know there's an easy way out there someplace?
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  #8  
Old 03-18-2010, 02:08 AM
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You could probably manually control the solenoid on the firewall by running a switch on it, but I think you'll have to fool the GEM into thinking everything is working as normal before it will shift the transfer case. I haven't looked to see how it is wired up.
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  #9  
Old 03-18-2010, 12:27 PM
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Thank you for the input so far guys! This is really encouraging.
@Tbear - one of the things I looked at before I read about the IWE was the "posi-lok" system made for previous generation f150s. It replaces the vacuum actuated system that engages the front drive shaft with a pull cable that gets routed into the cab.
Now, for your particular scenario I think such a system could be worked out if your were comfortable with some fabricating and making some permanent changes to the IWE system. It might be possible to rig up a system that pulls or pushes the IWEs in and out with a cable. Essentially the way that a mechanical parking brake works. Its a cable running to a center mechanism between the two wheels that pulls or pushes on the two sides equally.
With such a system the 4wd computers would all think everything is working fine, solenoid and all the vacuum stuff is still intact, just not hooked up to the IWEs. Instead the IWEs are manually controlled from the cab.
This would be the "next step" after seeing how simply locking the hubs by disabling the vacuum system works. Locking the IWEs is simple, just plug em up, but this would require some fabrication and more knowledge of the internal IWE workings than I have. But I'd love to see someone try it! Heck, make it a kit. I'd buy one.
Cheers!
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  #10  
Old 03-18-2010, 07:40 PM
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Quote:
Originally Posted by brianjwilson View Post
The integrated wheel ends do not take a load when shifting into 4x4. There is an electromagnetic clutch in the transfer case that brings the driveline up to speed, then engages the transfer case, THEN the hubs lock after everything is equal. The only time the IWE is taking a load shock is if you are spinning the tires while engaging 4x4. If the front driveline is spinning all the time (live axles) you should be able to engage 4x4 at any speed. That's how it worked on my ranger with manual hubs, and my sport trac with live axles.
the t-case clutch is only in AWD models.
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  #11  
Old 03-18-2010, 08:08 PM
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Quote:
Originally Posted by Paralyzer View Post
the t-case clutch is only in AWD models.
Then do you care to explain how the front driveline is brought up to speed when you "shift on the fly"?
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Old 03-18-2010, 08:12 PM
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Quote:
Originally Posted by brianjwilson View Post
Then do you care to explain how the front driveline is brought up to speed when you "shift on the fly"?
transfer case shift motor and syncro.
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  #13  
Old 03-18-2010, 09:17 PM
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Here is the text from my Chilton's manual.

Quote:
Originally Posted by Chilton's Repair Manual
The electronic shift-on-the-fly (ESOF) system allows the driver the same three ranges (2WD High, 4WD High, 4WD Low) as the MSOF system, and the same rules apply for shifting from 2WD High to 4WD High, and for shifting to 4WD Low. However, the means by which a shift is initiated are electronic: When 4WD High is selected at a switch on the dash, the Powertrain Control Module (PCM) receivers a voltage signal commanding it to energize the electromagnetic clutch inside the transfer case and the relays which energize the transfer case shift motor. When the shift motor reaches the correct position (determined by the position of contact plates which sends inputs to the PCM), power to the shift relays and motor is cut. When the transfer case front and rear output shafts are turning at the same speed, a spring-loaded lock-up collar mechanically engages the mainshaft hub to the drive sprocket, the front axle collar is engaged and the electromagnetic clutch is de-energized.
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  #14  
Old 03-18-2010, 10:09 PM
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your chiltons manual is wrong . only TOD (torque on demand) or AWD transfer cases have the duty cycled electic clutch. either way... the tranfer case is not desighned for the use the OP wants.

Last edited by Paralyzer; 03-18-2010 at 10:14 PM.
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  #15  
Old 03-18-2010, 11:37 PM
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Sorry, but the Chilton Manual isn't wrong. Or if it is, so is the Ford Factory shop manual and the Ford factory documents on the ESOF. :d Check on this forum, post number six links to the Ford Factory service documents, including "principles of operation" for the ESOF system and IWEs. http://www.f150online.com/forums/art...replacing.html

It only makes sense. If there was nothing to bring the front drive shaft up to speed then there would be a huge torque shock when shifting into 4wd on the move. And the reason the IWEs dont have any kind of clutch system is that they will be moving at roughly the same speed as the rear wheels when driving, so only the driveshaft and diff need to be brought up to speed. Disabling the vacuum and locking th hubs should theoretically have no effect on that system. If anything it may INCREASE the life of the t-case, because the clutch system will have less work to match the speed of the drive shaft to the rear drive shaft.
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Old 03-18-2010, 11:37 PM


 
 
 
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