4X4 Problem
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New User
Joined: Sep 2007
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4X4 Problem
My 99 SD has a auto hub lock problem. It locks up in lock position, but not in auto. I took the hubs off and check ok. I found crack vacumn lines at the hubs. I notice no vacumn pressure there. I trace it up to a switch under the hood on the right side. There is two vacumn lines on this switch. The top has vacumn and the lower line doesn't. I got a new switch from Ford today and install. It still does the same thing. Can anyone tell me what else to check? Thanks
Cargo Master
Joined: Aug 2003
Posts: 2,332
Likes: 442
From: Eastern Washington
search back towards last winter, common problem.
Most I've found to have torn diaphram in the hubs. You only get vacum there for a few seconds so you have to check right after moving the switch. Unplug the hose @ the hub on both sides and plug one with a golf tee or whatever fits. Turn the switch and see if you get vacuum at each hose, while the other is plugged. I think the lock signal is 10 sec and the unlock is 1 sec, but you'll figure it out pretty quick. You'll find more info with a search. Or, just lock the hubs and forget about them. Unlock in the spring. I leave mine locked all winter, it was worth about 1 mpg in my V10 on 38's, and .5mpg in my 7.3 on stock tires.
Most I've found to have torn diaphram in the hubs. You only get vacum there for a few seconds so you have to check right after moving the switch. Unplug the hose @ the hub on both sides and plug one with a golf tee or whatever fits. Turn the switch and see if you get vacuum at each hose, while the other is plugged. I think the lock signal is 10 sec and the unlock is 1 sec, but you'll figure it out pretty quick. You'll find more info with a search. Or, just lock the hubs and forget about them. Unlock in the spring. I leave mine locked all winter, it was worth about 1 mpg in my V10 on 38's, and .5mpg in my 7.3 on stock tires.
Cargo Master
Joined: Aug 2003
Posts: 2,332
Likes: 442
From: Eastern Washington
Hi!
Joined: Sep 2007
Posts: 1,268
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From: Central NJ
Blown fuse would not allow pressure in one hose and not the other, since you already replaced the switch i'm not sure, that what it seems would be the problem.
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I have check the power at the switch and have 12.2 volts. There is three wire going to the switch. They all have 12 volts. When I touch the front wire with a test light, I hear a click and vacumn is in the top hose. I wonder about a ground?? I need a wiring diagram for this.
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Junior User
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I've had the same problem with my hubs and all it took was a good cleaning theres like a diaprham in your hub that the vacuum pulls. some times it can get dirty and not work properly pull both your hubs completely off and go through and clean them with a lubricated cleaner like pb blaster or wd40 not brake cleaner it will eat the seals out it worked for mine good luck it only took me about 30 minutes