Unlocking auto hubs
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New User
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Unlocking auto hubs
Is it normal to have to rotate the hubs to LOCK and back to AUTO to get them to disengage? I've had the hubs apart, and there is a pair of metal tabs that once the vacuum has pulled them in, they travel past and over the plastic latch. Once the vacuum is removed, the tabs return to the starting position without pulling back the plastic plate. When you rotate the hub to lock, the tabs move forward slightly, latch on to the plate and draw it back alowing the gear to move and disengage. Does this make any sense? Seems strange to have auto engagement, and the you have to manually reset them to disengage.
Sit. Stay.
Joined: Oct 2001
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From: Washington State
No that isn't normal. Sounds like a little bit of maintenance is needed. Have you pulled them and cleaned & lubed them?
http://www.guzzle7pt3.com/allube.php
http://www.guzzle7pt3.com/allube.php
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They're assembled correctly and fully lubed. Can anyone explain what the purpose of the two metal tabs is? They basically hook and unhook the two plastic pieces together, but I don't understand why. It is when they become unhooked, that the force of the smaller spring overcomes the large spring and it holds the hub locked. When you rotate the hub from Auto to Lock and back it re-hooks the two plastic pieces, the smaller spring is captured and the larger spring can disengage the gear. Sounds confusing, but if you've had the hubs apart, you know what I mean.
Post Fiend
Joined: Mar 2009
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From: Mt. Shasta California
You shouldn't have to touch the dials. When it is in auto it is fully automatic and those hooks in the plastic unit and the unit itself is controlled by vacuum. If it doesn't work in auto there are about 4 things it could be. Lot's of info on vacuum in here if you do a search. The stock hubs are nice but require some upkeep.
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Thanks for the replys, I'm in the Northwest Subs of Chicago. I understand they are vacuum actuated, but when the vacuum is removed they rely on the spring to disengage. When the clips are un-hooked in the plastic unit, the smaller stiffer spring does not let the larger spring disengage the gear. One thing I have noticed, is when I switch the dial back to 2WD, I still have vacuum at the hubs. Seems to take a while to bleed off. Today I'm going to put a vacuum gauge on it and see readings I'm getting.
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Elder User
Joined: Dec 2007
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From: White Rock BC Canaduh
There is a time delay on the vacuum for the ESOF hubs. I tested mine recently and if I remember correctly,,, 5-10 seconds to engage and 10-20 seconds to disengage. Or maybe the other way around. I'm sure someone can chime in to confirm.
Rick...
Rick...
Thanks for the replys, I'm in the Northwest Subs of Chicago. I understand they are vacuum actuated, but when the vacuum is removed they rely on the spring to disengage. When the clips are un-hooked in the plastic unit, the smaller stiffer spring does not let the larger spring disengage the gear. One thing I have noticed, is when I switch the dial back to 2WD, I still have vacuum at the hubs. Seems to take a while to bleed off. Today I'm going to put a vacuum gauge on it and see readings I'm getting.
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From: Az
This is my understanding as well.
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Joined: Dec 2006
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From: San Diego, CA
That's correct. The vacuum is not continuously applied to maintain the hubs locked. It is only pulsed for around 20-30 seconds IIRC each time you go from 2wd to 4wd or vice versa. The vacuum required is not large (around 10" to lock and around 6" to unlock), but a small leak can cripple the ESOF system.
As for the vacuum taking time to "bleed" off, that shouldn't be a problem. It is only the initial "pulse" when the solenoid opens and a short duration of vacuum that is required to change the state of the auto-locking hub. There is no "relief" valve to speak of, so if you have a tight ESOF system it should take some time before the vacuum dissipates once the solenoid shuts. I would take the lingering vacuum as a good sign.
As for the vacuum taking time to "bleed" off, that shouldn't be a problem. It is only the initial "pulse" when the solenoid opens and a short duration of vacuum that is required to change the state of the auto-locking hub. There is no "relief" valve to speak of, so if you have a tight ESOF system it should take some time before the vacuum dissipates once the solenoid shuts. I would take the lingering vacuum as a good sign.
Post Fiend
Joined: Mar 2009
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From: Mt. Shasta California
I one of the 3 seals are bad; the black o-ring in the outer hub, the yellow o-ring around the hub casting, or the lip axle seal in the knuckle, then it can take the max time to engage/disengage. Sometimes I have to flip the switch on the dash again, as I am driving, to get it to come out.
Post Fiend
Joined: Mar 2009
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From: Mt. Shasta California
Thanks for the replys, I'm in the Northwest Subs of Chicago. I understand they are vacuum actuated, but when the vacuum is removed they rely on the spring to disengage. When the clips are un-hooked in the plastic unit, the smaller stiffer spring does not let the larger spring disengage the gear. One thing I have noticed, is when I switch the dial back to 2WD, I still have vacuum at the hubs. Seems to take a while to bleed off. Today I'm going to put a vacuum gauge on it and see readings I'm getting.
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Brian, your explanation explains it. I thought the vacuum is on the whole time the hubs are locked. The fact it pulses on and off explains why the plastic assembly un-hooks and the spring holds it in gear. I'm not getting the pulse to unlock it. Either that, or my unlock pulse is too strong and it's relocking it. From what I see, the lock pulse should be around 10" and the unlock 6". I'll have to check. Any ideas? How does the soleniod work, does the same solenode control both pulses? Thanks, John
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Joined: Jul 2002
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From: Long Island USA
Yes, the one solenoid does both pulses. It's around 40 seconds for the lock pulse, and 20 for the unlock.
Sounds like the solenoid isn't working correctly.
Put a vacuum gauge on the line going to one of the hubs and see what kind of vacuum you're getting, and report back.
Sounds like the solenoid isn't working correctly.
Put a vacuum gauge on the line going to one of the hubs and see what kind of vacuum you're getting, and report back.