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Diagnosing 4x4 problem

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  #1  
Old 03-10-2012, 03:26 PM
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Diagnosing 4x4 problem

I've done alot of searching and have yet to see really anything that matches what my 4wd system is doing. My truck is an '05 screw fx4, with the electronic 4x4 shift switch. When I shift into 4wd (hi or lo) the light on the dash comes on and the transfer case DOES engage, so the case motor works. I replaced the soilonoid on the fire wall with the new design and my hubs still don't engage. I have NO grinding or clicking noises like everyone else has described. I have 2 new IWE actuators on the way, but I'm not 100% sure they are the problem. This has happened once before, but it was under warranty at the time and all the stealership said was "we changed a couple parts, but it's working now" so I have no clue what they changed. Any ideas, I've got no clue???
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Old 03-10-2012, 05:06 PM
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go to the auto parts store and buy a vacum pump....i got one from auto zone for about 20 bucks...hook it to the vacum line coming out of your solenoid going towards your iwe's...pump it up...watch the gauge...see if it holds a vacum....really easy to do...
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Old 03-10-2012, 06:56 PM
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Yea, that's on the list of things to do. What has me puzzled is if I'm loosing vacuum, the hubs should "grind" or go ahead and engage. But I'm getting no noises or engagement from the hubs. That's the only thing that has me thinking that the IWE's may be frozen in the open position whether they have vacuum or not. Any other ideas?
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Old 03-10-2012, 08:02 PM
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Originally Posted by sethchid View Post
Yea, that's on the list of things to do. What has me puzzled is if I'm loosing vacuum, the hubs should "grind" or go ahead and engage. But I'm getting no noises or engagement from the hubs. That's the only thing that has me thinking that the IWE's may be frozen in the open position whether they have vacuum or not. Any other ideas?
It would be rare - but not impossible to freeze an IWE in the unlocked position. Having two of them do it is next to impossible. Are you sure they're just not locked instead? Jack the front end up and try turning each wheel. See if the half shafts turn. Do the same thing with the truck running. My bet would be that they're locked in (no vacuum) and you have a vacuum leak issue.
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Old 03-10-2012, 08:42 PM
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Theyre deffinately not locking in. With the truck off or running in 4wd I can freely spin the cv's with my hand. Also I know they're not locking in because I got slap stuck in the yard with a trailer the other day in 4wd, back end pulling front sitting idle. So if they had failed in the "locked position" my front would be pulling. I am also sure the transfer case is working, because when the truck was stuck I got out of it with it in Low still in gear. It was wet enough that the back tires were just turning in the mud so I took a peek under the truck and the front drive shaft was turning. Just can't remember if the front axles were turning. May go outside in a little bit and put it on jackstands again and take a look. Is there anything that meshes the front chunk with the front driveshaft? Maybe my driveshaft isn't engaging the front chunk!!!
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Old 03-10-2012, 10:08 PM
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Originally Posted by sethchid View Post
Theyre deffinately not locking in. With the truck off or running in 4wd I can freely spin the cv's with my hand. Also I know they're not locking in because I got slap stuck in the yard with a trailer the other day in 4wd, back end pulling front sitting idle. So if they had failed in the "locked position" my front would be pulling. I am also sure the transfer case is working, because when the truck was stuck I got out of it with it in Low still in gear. It was wet enough that the back tires were just turning in the mud so I took a peek under the truck and the front drive shaft was turning. Just can't remember if the front axles were turning. May go outside in a little bit and put it on jackstands again and take a look. Is there anything that meshes the front chunk with the front driveshaft? Maybe my driveshaft isn't engaging the front chunk!!!
No, the only disconnect on 04 up is the IWEs.
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Old 03-10-2012, 10:19 PM
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Worst case, I was thinking blown ring gear, but I doubt it.
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Old 03-11-2012, 10:10 AM
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Well, it definitely sounds like your IWE's are not locking in then. This post should help just in case.

Everything You Wanted To Know About The IWE System....And Then Some!

If you do need to replace them, make sure you check out the rest of the system at the same time. A vacuum leak or bad solenoid will take out a brand new IWE pretty quick. And if it's any consolation to you, changing out the IWE's is actually pretty simple. My first time out it took me about 45 minutes a side.
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Old 03-11-2012, 10:54 AM
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I picked up a vaccum pump last night from the parts store. I'm about to do a 6" lift, so I'll already have everything torn down, so I figured I'd go ahead and replace em then. But like someone said before, kinda seems impossible that BOTH have stuck in the "open" position.
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Old 03-11-2012, 11:28 AM
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Originally Posted by sethchid View Post
I picked up a vaccum pump last night from the parts store. I'm about to do a 6" lift, so I'll already have everything torn down, so I figured I'd go ahead and replace em then. But like someone said before, kinda seems impossible that BOTH have stuck in the "open" position.
Not if foreign matter or moisture had been sucked into the lines.
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Old 03-11-2012, 06:52 PM
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Ok, did a little looking this afternoon. I put the truck up on jackstands to get all 4 tires off the ground. Cranked the truck put it in drive, and let the rear tires just spin at idle. Thin I stopped them, put the transmission in N and switched the transfer case into 4HI, and shifted back into drive. Rear tires spin, front driveshaft spins (so transfer case deffinately works), and drivers side front axle spins (open dif), but no front tire movement.

Went ahead and shifted back to 2wd, and killed the truck. With the truck dead, and vacuum hoses removed from IWE, tire still spins freely (like it still has vacuum on it). Put my pump on each IWE, and they both hold about 22#'s. pulled both checks, 1 is bad, will replace both. Hooked 1 side back to the IWE and my pump to the other and cranked the truck. I'm reading on my pump between 20-23#'s on each side.

So where can I find these check valves? And what in the world is up with my stuff!?! Seems like everything is working but the IWE's. And what can spray into the lines to flush them, in case there is some debris in the lines. I'd hate to contaminate the new ones I'll be installing.
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