more esof
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Junior User
Joined: May 2003
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From: northport NY
more esof
My '03 F350 doesn't always go into 4wd when it's cold- like when it's been snowing. Sometimes it goes in if I back up, and sometimes if I turn 4wd off and then on again. The heater works right, and I replaced the vacuum valve a couple years ago ( thanks, FTE). I run it in 4wd for a mile or so when it rains and whenever I go on dirt and it always goes in. One of the posts on this said something about sending vacuum for 30 seconds. Is that to the hubs, so they have to hold it? The manual ***** are hopelessly stuck on my truck. I,d like to cure this- it's a real surprise to be in 2wd and not know it yet! Thanks, guys
Lead Driver
Joined: Sep 2007
Posts: 8,180
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From: Scio, OR
Sounds like your hubs are marginal or have a small leak.
First thing I think would be to follow Guzzle's hub cleaning procedure.
Welcome to guzzle's 4x4 Autolock Hub Lubrication Maintenance Web Page
If that doesn't work, then you're going to need a hand vacuum pump and gauge. Start by putting the pump on the hub nipple directly and pull down a vacuum of just over 8.75 in/Hg. This is what should lock the hub. Make sure the hub locks and that the hub holds the vacuum. If it leaks down you need to replace hub seals. Do this test on both sides.
You can do the same test by pulling down between 5.9 to 7.1 in/Hg. Hold that for about 30 seconds and release it. The hubs should unlock, but it might take a little bouncing around for the locking ring to come free. It can bind.
Then, I'd move to the line coming out of the PVH solenoid going down to the hubs and do the same two tests. This will tell you that those lines are holding vacuum.
You can also hook up your vacuum gauge with a T after the solenoid and have someone shift to 4WD. The PVH should apply more than 8.75 in/Hg to lock. Then have them switch to 2WD. After some time, the PVH should apply between 5.9 to 7.1 in/Hg to unlock. If this doesn't happen, you may have a bad solenoid, or a vacuum supply problem.
If your hub dials are frozen, it is likely that eventually the hubs are going to fail altogether and you will have to replace them. You might consider that for the future.
First thing I think would be to follow Guzzle's hub cleaning procedure.
Welcome to guzzle's 4x4 Autolock Hub Lubrication Maintenance Web Page
If that doesn't work, then you're going to need a hand vacuum pump and gauge. Start by putting the pump on the hub nipple directly and pull down a vacuum of just over 8.75 in/Hg. This is what should lock the hub. Make sure the hub locks and that the hub holds the vacuum. If it leaks down you need to replace hub seals. Do this test on both sides.
You can do the same test by pulling down between 5.9 to 7.1 in/Hg. Hold that for about 30 seconds and release it. The hubs should unlock, but it might take a little bouncing around for the locking ring to come free. It can bind.
Then, I'd move to the line coming out of the PVH solenoid going down to the hubs and do the same two tests. This will tell you that those lines are holding vacuum.
You can also hook up your vacuum gauge with a T after the solenoid and have someone shift to 4WD. The PVH should apply more than 8.75 in/Hg to lock. Then have them switch to 2WD. After some time, the PVH should apply between 5.9 to 7.1 in/Hg to unlock. If this doesn't happen, you may have a bad solenoid, or a vacuum supply problem.
If your hub dials are frozen, it is likely that eventually the hubs are going to fail altogether and you will have to replace them. You might consider that for the future.
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
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From: Stephensville WI
The key point is when you typed "The manual ***** are hopelessly stuck.."
Great indication that your hubs needs attention/maintenance/replacement. You'll know more when you get them off.
Great indication that your hubs needs attention/maintenance/replacement. You'll know more when you get them off.
Freshman User
Joined: May 2011
Posts: 27
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I have a 2000 F350. Is the clean up procedure the same for that year? When I replaced the front calipers and brakes lines I noticed that the vacuum hoses were dry rotted with holes and the nipples were rusted. I think there may be junk down in the holes. My hubs will rotate by hand but my wife would appreciate the auto locking feature.
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Junior User
Joined: May 2003
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From: northport NY
I put a gauge on the vacuum source today. When I switched it to 4wd, it went to 20-25" for 40 seconds, and then 0". When I shifted back to 2wd, it went up to 10" for 10 seconds, and then to 0. I couldn't find a tee, but I couldn't get anything to the hub with the little hand pump on the gauge, so I guess that means I know where to look for a vacuum leak?
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Lead Driver
Joined: Sep 2007
Posts: 8,180
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From: Scio, OR
What do you mean by "put it on the source"? Do you mean the side of the PVH solenoid that goes to the hub? If so, then it is working.
And by get anything to the hub, I assume you mean you hooked the pump to the hub nipple directly and could not pump down a vacuum. If so, then the hub seals are bad.
And by get anything to the hub, I assume you mean you hooked the pump to the hub nipple directly and could not pump down a vacuum. If so, then the hub seals are bad.
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Junior User
Joined: May 2003
Posts: 96
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From: northport NY
That's where I hooked it up. I'll replace the seals, maybe the whole hubs as soon as possible.
The manual ***** are stuck solid, so I can't get 4wd at all without the esof. Thanks- Lou
The manual ***** are stuck solid, so I can't get 4wd at all without the esof. Thanks- Lou
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