I've been troubleshooting my ESOF vacuum-operated hub engagement. I get the proper vacuum levels at the hubs with the vacuum hoses plugged at the hub, but with either hub connected to its vacuum line the vacuum is low. I think that indicates a vacuum leak in both hubs.
I have been unable to find any good troubleshooting techniques for finding hub leaks. The o-ring on the hub-lock mechanism appears to be ok. I don't know what provides the seal around the axle. Anyone who can help?
Use a vacuum pump with a gauge, hook it to the nipple on the knuckle, and pump it up. If it holds vacuum, it's good, if not, well... you get the idea
On the auto hubs, there is a white long rectangular "filter" in the middle of the ****. Cover it with your hand while checking if the hub holds vacuum. If that filter is leaking the vacuum, chances are the diaphragm in the locking hub is ruptured. If it still doesn't hold vacuum, it's most likely the knuckle seal.
The only diagnostic I am aware of for testing the actual hub seals is to use a hand vacuum pump attached to the hub itself to see if it will pump down and hold a vacuum. If it won't, one or more of the hub seals are bad.
Guzzle's 4x4 Needle Bearing Lube page is also a good reference on what it takes to tear down the hub to get to the rear vacuum seals.
I suppose the odd part is that the only ESOF problem I've ever actually dealt with in person was a bad shift motor relay. I just read a lot and use the service manuals and put it together.
I'd rather see a dozen helpful but redundant responses to someone than one post leading them in the wrong direction.
I had one problem with it myself, and it had to do with the latching mechanism failing. But having read the entire diagnostic procedure, and gone through it all with a pump and gauge, I'm the same way as you. Willing to help out because I understand the system.
Haven't had ANY problems with the transfer case in 8 years, just the hubs at 1.5 years after purchase, and decided to put on Warns. And use Termalene grease on the needle bearings (one was rusty when the hub itself went south). No problems since.
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