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Auto hubs - vacuum problems, questions

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Old 08-19-2018, 12:50 PM
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Auto hubs - vacuum problems, questions

I rebuilt my front end and am not getting the auto locking hubs to lock in. does anyone know the spec for the vacuum pressure on the system? I imagine both sides are on the same circuit (a leak anywhere would cause both to not work).

I am thinking about hooking up an AirLift to pull vacuum on the circuit. Is there a risk of damage with too much vacuum? Or is the AirLift likely to not be able to draw enough vacuum to get to that point?
 
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Old 08-19-2018, 09:37 PM
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Problem fixed. One of the axle shaft seals dismounted from the axle. Pressed it back on in a hydraulic press then hammered it back in to the knuckle.I tested each side individually. Passenger side hub worked, drivers side did not. So I went down the path of concentrating on the drivers side. First up was the rebuild kit for the hub. Nada. Out came everything and the seal was obviously off the axle when the hub came off.

In any event, back in business.

I'd still be curious of the pressure spec.
 
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Old 08-21-2018, 01:19 PM
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Not sure of the pressure spec, but I was going to recommend checking your outer axle seal; sounds like my guess would have been correct! Always good for my ego!
 
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Old 08-21-2018, 09:44 PM
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I knew that was important... I just wanted it to be something else. Although, getting to it now with all the parts coated in never-seize makes it quicker to get to.

For what it is worth, how I diagnosed it the other day was by disconnecting the air line on one knuckle at a time and plugging it. I used a seal pick as the plug. I manually locked the disconnected airline hub and left the other side in auto. Then I cycled the 4wd selector.

This method proved two things at once - what side had the issue and that, with the non-functional hub disconnected, the rest of the vacuum circuit was fine. If it wasn't the other side would not have engaged - if the line was leaking at the solenoid, for example.
 
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Old 08-22-2018, 06:20 AM
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you probally have a leak at 6 oclock position on hub housing ....theres a large nut and bolt stud there...put a shot glass of grear oil in the fitting where the hose connects and see if the oil drips out of the bottom.
 
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Old 08-22-2018, 08:34 AM
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Originally Posted by KC8QVO View Post
I rebuilt my front end and am not getting the auto locking hubs to lock in. does anyone know the spec for the vacuum pressure on the system?
It's been a long time but I think the vacuum numbers are 10" and 6". I don't remember which is for locking and which is for unlocking but the pulse is for about 30 seconds IIRC.
 
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Old 08-22-2018, 10:25 AM
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Originally Posted by brian42 View Post
It's been a long time but I think the vacuum numbers are 10" and 6". I don't remember which is for locking and which is for unlocking but the pulse is for about 30 seconds IIRC.
Vac both ways? Or vac to lock and pressure to unlock?
 
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Old 08-22-2018, 01:32 PM
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Vacuum both ways. Vacuum pulse to lock and vacuum pulse to unlock. Can't remember which is the higher value though (my gut tells me that it's 10" to lock and 6" to lock).
 
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