Just replaced IWE's AGAIN. Tires free wheel normally at low speed with no load on engine. The moment I hit a hill/incline (put a load on the motor) the hubs start making that god awful. I believe the check valve closest to the solenoid is the issue, cause I can blow air in both directions through it. Additionally a ton of dirt also came out of it. So I then proceeded to blow out the vacuum lines going to each IWE . But the Same issue continued. When I pulled the other check valve it hissed as if air was escaping.

I even isolated the solenoid from the equation with no change.

So the question is will a bad check valve, closest to the solenoid, produce the symptom I described?

 

Have you read this thread?

https://www.f150online.com/forums/ar...then-some.html

 

Yup, no where in does it say "a bad check valve will result in partial engagement of the IWE when a load is placed on the motor"

That is the burning question

 

Logic tells me if the check valve is bad, vacuum will drop when accelerating and possibly cause partial engagement. Logic also tells me that if the check valve is bad, it needs to be replaced anyway!

 

I'm thinking the same thing....gotta move heaven and earth to get one. Nobody has them in stock

I just pray it's that simple

 

I have wondered if these would work...

http://www.usplastic.com/catalog/ite...3369&catid=489

They are cheap...

FWIW...

 

With winter coming - till you can find check valves, why not just cap off the vacuum and leave the IWE's engaged?

 

Ordered one from Amazon .... Should be here on Thursday . I probably will do that.

 

My '05 had three in the line. I used two of these: and for the larger one next to the brake booster I used this:
and yes, bad check valves will cause partial engagement of IWE's under load.

 

Thanks fellas... I'll let ya know if it works.

 

I had the kind of the same problem and it turned out to be bad check valves in vacuum lines for the 4wd. Was letting the hubs engage when driving causing the front drive shaft to spin with out being in 4wd. I replaced the Solenoid,Line assembly w/ one check valve in it, and Check valve that goes to the engine. My problem went away! I pulled them off and blew thru them in both directions and they blew both ways=BAD VALVES
I would replace all of these to fix it. http://www.ebay.com/itm/BRAND-NEW-FORD-F-150-OEM-LOCKING-HUB-VACUUM-TUBE-4L3Z-3A788-AA/221682987087?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140602152332%26meid%3D025450fc129f499fb905b0cc64f45e25%26pid%3D100011%26rk%3D5%26rkt%3D6%26sd%3D281665586895Motorcraft #YG360
Vacuum Check valve to the motor $11 (also called Ac control valve!)

#XR3Z-19A563-AA & E4EH-19A563-AA
Vacuum line assembly with one check valve. $10
Got both off ebay

 

Just get an entire new 4x4 vacuum line assembly. Get the motorcraft one comes with everything you need. Picked mine up from a dealer I get odd parts like this from for $15... Fixes any hidden issues you could have. Changed my lines in my driveway in 5 minutes. Just run the new line next to the old one (runs along a cross member of the frame). When I changed mine I got a lot stronger vacuum at the ends that go into the hubs, but my hubs still wouldn't disengage completely, telling me the bladders in my hubs are shot.... Waiting for some more cash flow to get new ones