Common problem I know. In spite of all the good diagnostic stuff here, I'm still stumped and need help.

So far, I've tested:
1. The Transfer case motor. I can turn front shaft in 2WD, can't turn it in 4WD.
2. The front wheels freewheel rather in 2WD 4High or 4Low and when vacuum line from IWE is disconnected.
3. IWE solenoid. I get 21 inches of vacuum in 2WD and 0 vacuum in 4WD. This is at the first connection of the solenoid's vacuum output port.

Where do I go from here? If there was a vacuum leak anywhere downstream, I wouldn't get the 21 inch reading, right? Is it possible the hubs are stuck in 4WD and the vacuum isn't disengaging them? How do I check that?

Thanks in advance.
John.

 

How do the hubs work with the engine running? They could be stuck disengaged.

 

The are the same as with the engine off. One additonal item. I have found that the passenger side half-shaft spins with the tire and the driver side half-shaft does not.

 

I believe you found your problem.

 

At the risk of sounding ignorant, please fill me in in.

 

Engine running, truck in 2wd, both half shafts should spin freely. Engine off, half shafts should not spin freely. If only one works like this, the other one is "broke". Does yours do this.

 

First, thanks for the replies.

Yes, basically the driver side half-shaft never turns when I spin the wheel, pickup running or not, 2WD and 4WD. The pass. side always turns when I spin the wheel. Have any idea what's broken?

 

With the engine off, if the halfshaft does not turn when you spin the wheel, the IWE is bad. With no vacuum, both IWE's should be locked. When you apply vacuum, they should unlock.

 

Does this mean I have one IWE stuck disengaged and one stuck engaged?

 

Found my own answer. For those who may have the same problem:

The hub vacuum seal can also fail. This usually results in an engaged (half shaft locked to hub) IWE on the problem side, and low vacuum on the other side. Thus, your grinding sound might be coming from the good IWE. This is bad because the problem IWE has to be replaced and if not fixed quickly will destroy the good IWE on the other side- requiring replacement of both. You can remove vacuum from the system by disconnecting the vacuum line before it gets to the reservoir (and depleting the stored vacuum in the reservoir by disconnecting the check valve) This will lock the half shafts in 4x4 mode and won't hurt anything because the TC is still unlocked, but might stop the grinding of the IWEs and hubs. This is somewhat of a design flaw in the system that allows this- both IWEs get their vacuum off a single line from the IWE solenoid.

 

This sounds very similar to the problem I am having. The only difference is I've never had any grinding. How difficult is it to replace the IWE's?

 

Have you read the threads I linked you to in your thread? One of them specifically addresses IWE R&R.