Read everything I could and couldn't find a problem/solution similar to mine, so I'll try to keep this short since A) there are enough 4wd threads here and B) I don't want to lose anyone's interest before getting some help.

- Replaced broken (in three pieces) actuator on driver's side. Also replaced hub assembly (bearings went bad). Afterward started getting the grinding noise all the time in 2wd that goes away in 4HI.

- Replaced the entire hose assembly since I was not getting vacuum at driver side end hose. Still wasn't getting vacuum, turns out passenger side actuator diaphram was completely torn up as well (checked vacuum with hose on passenger actuator, not removing and plugging like I should have), so replaced the passenger side actuator too.

- Driver side grinding noise went away completely, now getting grinding noise on passenger side ONLY WHEN PRESSING ACCELERATOR. Take foot off accelerator and coast down road/highway noise goes away. Noise also goes away when putting truck in 4HI.


My latest actions: I've checked vacuum at both ends of hose while someone in park throttles truck up to 3k rpm, vacuum doesn't appear to change at either hose end while opposite side is attached to its actuator. Replaced passenger side actuator again thinking the first was defective, no change in grinding noise. Greased ring on wheel hub where actuator attaches thinking I was getting a leak at the actuator/hub seal, no change. Still only a grinding noise when accelerating, not while coasting with truck running.



The perplexing part: If it is a vacuum issue, how is it I am getting good enough vacuum from the driver side but not from the passenger side, since the driver side hose connection is downstream from the passenger side? Also, how am I not seeing the vacuum drop when checking at the hose end of either side while someone throttles truck up in rpms?



My thoughts: Definitely a vacuum leak somewhere in the system, minor enough to not notice right away on gauge, thinking to check the vacuum box and check valves next. Also thinking the passenger side hose from solenoid has a small leak causing the issue on the passenger side and not the driver side anymore, so thinking of putting the old hose back in to see if there is any change (I had replaced the hose prior to knowing the passenger actuator was torn up so I am not sure if the hose is really bad).

Any other thoughts people have I am happy to hear.



3-piece actuator I described above in picture for reference. Honestly I was not surprised, this has been my luck with this truck.

 

From the IWE post on main page --- check the check valves ??


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.

 

Thanks for the explanation, this makes sense to me. Two check valves ordered up (they're cheap enough I'll replace both and see what happens). I'll post up in a few days what the result was.

 

I replaced the two check valves this morning, unfortunately there was no change in the grinding of the gearing from the passenger side actuator after changing them out. Made sure the valves were in the correct way (changed them with truck running to be sure of airflow).

What bothers me is that it is ONLY the right side that makes the grinding sound in 2WD, and it only does it under throttle. If the system was losing vacuum somewhere, wouldn't it affect BOTH actuators since the vacuum is not independent to each side? It also bothers me that even while truck is rev'd to 3k RPMs and the hoses are checked one by one at the hub I am still getting ~20psi... Though I can try to rev higher to open the throttle as though the truck were racing down the road as opposed to just sitting in park/neutral.

Only other part I can think of to change would be the vacuum box itself but I am doubtful that is the issue. Truck may have me beat and a trip to the dealership is my next move, unless someone can think of something that I am not.

 

maximum vacuum is trapped in the IWE end by the check valves... If the truck is quiet EXCEPT when you stomp on the throttle, it would SEEM like the motor looses vacuum and the check valve is not holding on the right side, OR THE HEAD IS LEAKING vacuum out ? If check valves are holding, then I agree the problem is PROBABLY at the IWE head.

 

I'm hoping by "head" you mean at the actuator/hub and not the head on top of the engine (attached to the headers)... Otherwise for now I'll just rig to use 2WD and 4LO, and eliminate the 4HI option.

My next plan of attack is to replace the hub assembly on that side. After replacing the actuator (twice) and check valves, and the fact that the driver side is not grinding at all, it's the only other part that I think could be leaking vacuum from the system, and would affect the passenger side only if it is just a slight vacuum leak when under load.

*I haven't driven the truck far enough (up the block and back, throttle on and off) to know if the slight leak on passenger side would eventually affect entire system and driver side would eventually start to grind... Just another thought as I work through this.

 

Well, just pull the hoses off the IWE's and plug. Then it's just like having your "hubs locked" all the time. Not really a big deal (but it's not the correct way to fix this either, solely because of mileage concerns, really).


Anyway, if you engage 4wd when the front wheels are elevated, how quickly do the IWE's lock in (assuming you're not on the throttle)? How quickly do they disengage once you shift to 2hi?

 

Thanks for the reply and suggestions. I thought of just plugging the hoses at the actuator ends, but isn't that just like turning on 4HI all the time? I thought that was bad for the axles/wheels/differential/tires as well as gas mileage (gas mileage I don't really care about, but I don't want to completely destroy an already damaged truck - not ready to buy another one yet). Also I don't think this would solve my P0171/P0174 lean codes if there is a leak somewhere in the system (see below - I think it's the vacuum reservoir, or accompanying hose to/from it).

I haven't attempted to time the engaging/disengaging of the actuators, I wasn't really sure how fast it was supposed to happen. I did however have someone start the truck while I had a vacuum gauge on one hose at a time and noticed that while the gauge did get to ~20psi it wasn't like "BAM!" it's there immediately. More of a semi-gradual pull to get from 0-20psi (maybe a second or two?).

I did replace the second hub assembly. No change, but as bad/broken as the first one was and as rusted and corroded this one looked it probably wasn't a bad idea to change it out as well, also considering the bellow on the actuator attached to it was ripped apart and water probably soaked the inside of the actuator and hub pretty good over time.

A noted test: I drove the truck for longer than a few seconds on throttle and farther than up the street and back. Turns out while the passenger side actuator grinds first and almost immediately, the driver side also does start to grind as well over time. My last item to change out is the vacuum reservoir (a relatively cheap and easy fix compared to all the other broken parts I've had to replace) or the hose running to it. At this point I am fairly convinced I have a leak/crack in the reservoir, as I am still also throwing both bank1/bank2 lean codes after significant driving. Air being sucked in slowly through a reservoir crack over time would probably throw these codes I would think.

Vacuum reservoir box on order, should be delivered in a couple days.

 

No! Your IWE's do not at all decide if you're in 4wd. Your transfer case dictates that. The IWE's locking in is just the next necessary step to make sure that once the t-case chooses to send power to the front driveshaft (which then travels through the ring and pinion to your halfshafts) that power is then translated to the front wheels.


If you leave your IWE's locked it just means your front half shafts spin all the time. Ever driven or owned a front wheel drive car? Guess what? Those half shafts spin 100% of the time. edit: even certain manufacturers of IFS 4wd allowed half shafts to spin at all times if there's a CAD - central axle disconnect. GMT400, 800 and 900 come to mind. Dodge also allowed front u-joints to spin at all times, too, even on a live axle from '94-02 also employing a vacuum CAD


It also means your front driveshaft will spin all the time. Guess what? Your rear driveshaft already spins every second you're rolling, even coasting.


There's nothing wrong with leaving the front driveshaft (and correspondingly, the front output on the t-case) spinning. Truly, the ONLY reason we've designed in lockouts (aka locking hubs or in this case IWE's) is to reduce that parasitic drag and slightly improve mileage, and possibly reduce NVH to in turn reduce complaints from soccer moms.


In the late '70s Fords with the NP203 simply came with drive pucks - literally a puck that mated wheel bearing hub (and thus the WMS/wheel) to the axle shaft itself. Locking hubs/lockouts are just sliding drive pucks that allow the user to decide when it's engaged and disengaged. An IWE is also just a sliding drive puck that defaults to locked with no vacuum, unlocked when vacuum tells it to slide away.


But as for your lean condition...........yeah it'd be nice to fix that.


I'm sorry to get sidetracked but it amazes me how few people understand the 4wd system of any truck which is still - for the most part - very simple.


Anyway, please post your resolution when you find it. Keep up the good fight!

 

Thanks for the info, though I probably could have done without the condescension that came with it.

Went to install the vacuum box, found out the vacuum hose running from the vacuum box was cracked almost in half. Ordered new part. Part# is 4L3Z19C828AA.

 

Those hard plastic vac line faults / cuts / etc ..... can br cut out and replaced with short rubber hose.

 

how did it get cut ?

 

Unknown. Not the first owner. 4HI has never worked right since ownership (what do you want for $8k under KBB at the time and buying from a "multi-colored triangle flags display" used car place). Only discovered all the other problems after fixing the driver's side actuator and having that one grind all the time.

I'm sure I could have rigged something up with vacuum hose and connectors, but for $24 (new/taxes/shipped) I used the actual part, and came with new check valve (oddly enough was not one of the check valves I replaced myself when I did check valves last week, this one was buried behind the PCM and I thought the two I saw and changed out were the two for the 4WD IWE system). Though if this one breaks I'll go the route of replacing the plastic lines with vacuum hose tubing.

Side note: truck felt completely different, this probably solved my annoying P0171/P0174 lean code issues as well - time will tell in a few days after a few trips. "Felt" more powerful at idle, idled correct with no fluctuation, no CEL, drove smooth, trans shifts felt buttery smooth like i have never felt in the truck (most of the time shifted "odd" in an up-down-highrev-up type sounding shift when going from 2nd to 3rd when casually lazy/slow driving around town).

Simple fix may have solved three of my major concerns with the truck.

 

Ok so what I thought was a fixed 4wd system is not quite as fixed as I would have hoped. If driving around town, everything "seems"
normal, however if I am on the highway (or driving for a long time on a straight road) and have the throttle open for longer than about a minute or two, the grinding noice comes back. It goes away once my foot is taken off the gas pedal, and remains quiet under acceleration again for a minute or so.
There's still a minor leak in the system somewhere. And of course my CEL is back (P0171/P0174 lean banks 1 and 2).

Before giving up, My last plans of attack are:

- replace the lifetime warranty iwe solenoid (is it possible that this could be leaking?)
- replace the "double hose" tubing part coming off the colenoid and running to the two connections of the system that it hooks into
- replace the tubing from the engine to the above part
- replace the entire tubing running to the two actuators from the part above

After that, I'd have to say that it would be time for the pros.

For the time being I tried your method of unhooking the tubing directly attached to the actuators. Wow, loud grinding noise city, right from the first motion of the wheels, that never goes away as long as the truck is in motion. So either:

- There is something wrong that goes deeper than I am looking with the truck and the 2wd/4wd system, or
- you have no idea what you're talking about and only report what looks like it should work on paper.

Have you actually tried the method you describe about unhooking the actuators from the vacuum lines and letting the actuators spin with the front diff., or is it just what "looks like it should work" based on a drawing up of the system?

Disclaimer: Not trying to pick a fight, just trying to get to the bottom of the situation I have and correct info posted in this thread for future F150ers that may be reading this post looking for their own solutions.

 

I replaced my IWE actuators @ the hub 3 (maybe 4) times. Each time other than the last I packed the ends with grease - packed isn't the right word, but I greased fairly heavily.

I also replaced the solenoid, bought check valves but I don't think I ever saw where they went, I replaced both front hubs.... They'd last about 3 months & then make the sounds/have the symptoms (grinding noise) similar to what you're having.

This last time, sometime around mid/early March this year, I just cleaned the gears on the hub & very lightly greased them. The only thing I could think of was that the grease was getting too cold/stiff and not allowing the actuators to move back & forth as easily. I park outside, live in UT, and I drive the truck up the canyons 2-3 times per week to ski. I don't use the 4x4 much, I hope it lasts this time - it's been frustrating to me but I think I've got it. I remember parking in 4x4, in deep snow, when I think I heard one give.