I've done all the IWE checks and everything operates fine and I have vacuum at the hubs and they lock and unlock normally. It sounds just like all the video's of others with IWE problems. Only difference is even if I put it in 4x4 it still makes the noise. Only does it with load on the motor. Does it in every gear except N (no load no noise) I've checked the heat shields nothing is coming in contact with drive train.

Anyone have some ideas or possible causes?

 

did you take out the IWE and look at it?
I had one that was stripped out, had to replace the hub and the IWE both
previous owner must have driven it a long time for it to get that bad

 

Nope, but I ruled out all the easy stuff so I guess its time to start pulling things apart. The trans is due to be rebuilt and the diff fluid needs changed. Plus I've been overloading it quite a bit lately due to building a garage so It could be trans, TC, Diff. or the IWE. All of which get progressively expensive. I did get the Vacuum gauge out. Something I'm not clear on is do the IWE's drop Vac over a period of a few minutes? I tested a new one from the store and it does the exact same thing as the ones in the vehicle no bleed down at all from the engine to the hubs but the IWE's will start at 20 and drop to about 10 in about a minute. Only difference is the new one isn't actually installed and sealed against the hub. I'll look at all the sticky's and read through all the IWE posts. I swear the sound its coming from Under the cab near the transfer case. Why I was leaning towards trans issues. Cant really tell very good as I'm straight piped so its hard to distinguish where the sound it coming from for certain.

 

Shouldn't bleed down like that. Especially that much in a minute. I just had to trouble shoot one and at 20 lbs it didn't bleed down in 5 minutes. Are you testing right at the IWE or from the vacuum lines up top? If you wanted to prove the hubs just unplug the IWEs at the tire. This will engage them and there will be no vacuum to try to disengage the hubs. So if this quites everything down you can rule out any high dollar issues like the transmission. Let us know.

 

my left iwe was seperated in 2 pieces the vacuum worked fine but was not attached to the locking mechanism so that side was always locked in but tested good for vacuum
my right side would bleed down quickly and click sometimes when driving, when vacuum was low it would click and in 4x4 it clicked all the time because it was worn out.

one test is to just unhook the vacuum line from the IWE, it should then be locked in all the time at that wheel, will not be in 4x4 as long as the switch is set to 4x2 because the transfer case isn't shifted.
if you unhook both IWE's the hubs should be locked and make no noise.

 

If you only unhook one of the IWEs you have to plug the line. If not it creates a vacuum leak and causes the other side to grind.

 

 

Here is the video
Ordered a set of IWE's but as you can see in the video they work flawlessly. except for the slow bleed down. and a bad check valve. I have the parts so I'm going to replace them anyways as I did find out what the issue was see below

I put the cam on the diff just to see and it was definitely coming from it. So I pulled it apart no shavings. But the wheel bearing were a little sloppy so I went and got some of them. And while i was doing bearings I might as well get the rest for the diff. 130k its probably due. BUT while I was in this process I realied I had a U-joint that exploded... SO long story short +$400 later it was a dang U-joint!

At least I know going forward these are all new... What an adventure. First time I actually had to do something on this truck in 12 years more than change the oil. Funny thing is I replaced the U-joints a year ago along with a new driveshaft (broke it trying to press out the old stock joints) Why It didn't even dawn on me to check the U-joints
U-joints
Front wheel bearings
Rear wheel bearings
IWE's
Diff rebuild
Tie Rods
Ball Joints