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Discussion Starter · #1 ·
Just as the title of this states, my truck will go into four wheel drive only when it feels like it.
I bought the truck, 2003 ccsb 6.0, in July. I never thought of checking the 4wd when it was +35*C. All I was concerned about was the AC!!
Anyway, up until a month ago, nothing. The 4wd light would come on when I start the truck, but that's it. I'd often try the switch, more out of bordom than anything. Then one day the light came on and I could hear and feel the strain of 4wd engaged. I might switch it in two or three times in a row, then nothing for a few days.
I left work today in 4wd, being the first time I really used it being that we're in the middle of getting ten inches of white depression. I came home. Good. I was home for about an hour. Started the truck, still 4wd. I'm getting excited. When poking around the city. Still good. Went through a drive-thru for a coffee. Had to turn the truck off at the speaker. Started the truck. 2wd. This is when I came upon this forum; parked on a city side street, doing a Google search. I found the great write up that someone had done, so I checked all the fuses, switched the relays around... still nothing.
I can understand the procedure if there's nothing to go on, but what can I do to track down the attitude problem that is my intermittent four wheel drive? I'm at a loss.

Sorry for the story, but perhaps it will help in building a baseline.

Thank you, in adance.

Morley
 

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This winter I had bad relays in my 08 and 02 causing intermittent or no 4x4 engagement. Cheapest fix I've ever had.
 

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My understanding is that if the light is coming on the relays are working because the light is activated by a switch inside the transfer case. If your truck has shift on the fly then you likely have a vacuum problem. But you should be able to lock the hubs manually which will give you 4WD - it just won't disengage the hubs when you switch out of 4WD.
 

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+1 to what bob said. Every superduty I've had has eventually, and generally quickly, developed a vacuum leak in the hubs. It seems a universal problem. I got tired of wondering if it was going to engage, or having it slam into engagement after the back wheels were spinning, so I treat them like manual hubs.

I had issues with my 2000 not engaging at the T-case, and it turned out to be the GEM module. I was having crazy issues with the power windows and locks because of the same issue. Windows would only work if you held the door "Lock" button; Horn would honk when you hit the door "unlock" button, etc.
 

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Discussion Starter · #6 ·
Right, but the issue is the light hardly ever comes on. When it does, there's 4x4.
I may just be driving down the road, flick the switch and everything good happens. Most times, however, nothing.
Example: I was just at my range. The road and parking lot are snow and ice covered gravel. When I was leaving, I wanted to pop down one of the side roads to say good bye to a friend. Chancing it, I turned the dial to 4x4. Light on. Four wheels engaged. 200 ft later, the light went out and the truck went back to 2wd. I've had the truck turned off twice since then. Still nothing when I turn the dial. My hubs ARE in manual, as I know I have the drivers side line clogged.
 

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Doesn't that sound more like a bad electrical connection rather than mechanical or pnuematic?
 

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Discussion Starter · #8 ·
Yes, that's what I'm thinking. I was told that it could be the dash switch, but I wonder if I just bite the bullet and get a new silonoid and two new relays. ...
 

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I'll expound since I was basically told I'm wrong. 2002- start truck 4x4 light comes on, goes off with truck in 2wd, like it should. Turn switch, nothing clicks, bangs, or chirps. Switched 2 relays under hood for 4x4 engagement. Now when started, 4x4 light on then off, turn switch 4x4 engages. Yay. Back to 2wd - nada, stays locked in. Switched back, back to original issue. Replaced both relays with new relays, everything engages and disengage as it should.

2008 - took into shop for grinding and intermittent engage into 4wd.light on dash on then off when starting. Light just blinks on dash with turn of switch, usually. Sometimes engages with no rhyme or reason. Pay $800 in modules and get truck back, same issue. Take back in. Replaced $15 relay and all works fine. They said, bad ground on relay. Were modules really bad? Don't know but have new mechanic now.
 

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I'll expound since I was basically told I'm wrong. 2002- start truck 4x4 light comes on, goes off with truck in 2wd, like it should. Turn switch, nothing clicks, bangs, or chirps. Switched 2 relays under hood for 4x4 engagement. Now when started, 4x4 light on then off, turn switch 4x4 engages. Yay. Back to 2wd - nada, stays locked in. Switched back, back to original issue. Replaced both relays with new relays, everything engages and disengage as it should.

2008 - Replaced $15 relay and all works fine.
I am not having problems with my 2000...yet... but I am filing your post away for when I do.

Thanks :thumbsup:
 

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Discussion Starter · #11 ·
Well, that was relatively cheap. 48.00 for two relays. Didn't change a thing though.
 

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Well, that was relatively cheap. 48.00 for two relays. Didn't change a thing though.
Dang.

So if relays are good and fuses are good, whats the enxt thing to troubleshoot? Is there a way to inspect the dash switch without buying a new one?
 

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Discussion Starter · #13 ·
I don't know much about vehicle electrical systems. Although, I figure that I can pull the switch and check it via the pins with an ohm meter.

I priced up the solinoid while at the dealership. 118.00tx for that. ...
 

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Just had similar problem on mine. Everything fine then no light, no 4wd. Electric motor on transfer case bad. (Range selector) My local dealer wants $530-ish for the part. Maybe...
 

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Gem module maybe.. 150-300 depending on new or used on eBay. Then that switch is around 30 but you should probably check power to your t-case to make sure it's not a connection issue.
 

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From all I'm reading, gem modules were phased out in the 7.3 trucks. 6.0 trucks use 3 modules, the 2 in question would be the Vehicle Security Module (VSM), or the 4x4 module. Seems to be alot of conflicting info out there so not sure what's accurate. My guess is one of these 2 or something is loose because your problem is inconsistent.
 

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Discussion Starter · #17 ·
Thanks! Yes, the gem would be for the 7.3. It's good to know what the others are. Perhaps Google can point me to where they are and I can check. It could very well be a loose plug somewhere. Sure wish I had the 4x4 yesterday, with the four hours of freezing rain followed by six inches of snow. The Mickeys on the back got a work out. Lol
 

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Your hub solenoid is on the passenger side inner fender right behind the battery, has a 3-wire connector & 2 vacuum lines. From what I've read after many hours searching the VSM is bolted to the back of the dash behind the radio, & the 4x4 module behind the glove box. I googled "location of 4x4 module on 04 super duty" & found 2 separate items on Just Ask that had alot of info, diagrams, etc. Sounds like VSM issues show much like GEM issues (other electrical weirdness) so I'd lean toward the 4x4 module. In a pinch you can remove the motor from the t-case, put a baggie over the 2 elec connectors & zip-tie them out of the way & engage 4wd with a wrench. Not ideal for sure but works if you need it.
 
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