automatic hubs not getting vacuum
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automatic hubs not getting vacuum
My f350 auto hubs are not locking. Was told hubs not getting vacuum. Light comes on dash saying I'm in four wheel drive but hubs have to be moved off "auto" setting to "lock", then works fine.
Any idea why no vacuum or what to check?
Any idea why no vacuum or what to check?
Postmaster
Joined: Sep 2008
Posts: 3,220
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From: VA
I would bet on the hoses or seals are gone in the hub. Turn your a/c on hi and see if it ends up going thru the defrost vents .Then you definitely have a vacuum leak somewhere.
You have 3 "seals" on each hub. The outer hub o-ring, the inner yellow o-ring and the large knuckle seal on the back of the hub.
Hoses are simple and cheap to replace so I would start there for sure.
You have 3 "seals" on each hub. The outer hub o-ring, the inner yellow o-ring and the large knuckle seal on the back of the hub.
Hoses are simple and cheap to replace so I would start there for sure.
Post Fiend
Joined: Mar 2009
Posts: 11,798
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From: Mt. Shasta California
After checking the hoses etc., take the hubs apart, clean and grease them to elimate any problems there. I re-used the black outer o-ring after cleaning it with WD40 and greased it with white grease. I also used a screwdriver on the snap rings as I couldn't find my SR pliers. Mine is smoother now and I became more familiar with how it all works.
You won't need to remove the other seals mentioned above for this job, but you will as a last resort.
You won't need to remove the other seals mentioned above for this job, but you will as a last resort.
Posting Guru
Joined: Nov 2005
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From: Wyandotte, Michigan
My hubs don't lock in either but I am getting vacuum down at the hubs. I am guessing that my orings are leaking but the air works fine out through the vents. I have new hubs and locking hubs to go on when it gets closer to winter time. Hopefully that cures it.
New User
Joined: May 2009
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Does anyone have a pic of the inside of the spindle where the hoses hook up? On my F350 there are 3 hoses on the back, one being the brake line the other being the vacuum line what is the other line??? I guess the smaller hose is the vacuum line.
Logistics Pro
Joined: Aug 2007
Posts: 3,974
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From: Millersburg, OH
The other wire is ABS sensor. It will go off towards the frame to a connect on the back side of the wheel well cover. The vacum hose will go up to a braket and connect under the brake line. The brake line will go down to the caliper.
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Post Fiend
Joined: Mar 2009
Posts: 11,798
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From: Mt. Shasta California
Did you ever take them apart? Sounds like they need a clean and grease..........didn't see that you have new hubs coming
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Posting Guru
Joined: Nov 2005
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From: Wyandotte, Michigan
No, they are the newer style that no one knows how to tear down yet. The ones with the screws. I have new auto hubs next to my desk along with new unitized hubs. Waiting on my new rotors, pads and ujoints.
Postmaster
Joined: Sep 2008
Posts: 3,220
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From: VA
Im gonna take a stab that its the knuckle seal. Mine was nearly destroyed but my A/C worked fine. I also had no yellow o-ring installed and the grey plastic deal was installed on the wrong side of the hub. All fixed and it works. Spent a few hours and like 65 bucks. (all new seals on one side)
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