[JakeFeyen]

okay, so i have a 1999 Ford F350 superduty DRW 7.3 Powerstroke. i bought the truck about one year ago and the 4x4 has worked great, just recently it become very finicky, it works sometimes and it doesn't others... when it works the 4x4 light comes on and it is as if nothings wrong. When it doesn't work, there is just simply no response, no light... nothing.
Would this be a bad relay, and if so which relay is it? any ideas?

thank.

 

[jeepwillys]

I believe there is a relay thats on the transfer case see if you can hear it clicking in when its not working or test it with a meter. Might even be the connection itself, might check that. If it is clicking in then you might have a vacuum leak somewhere.

 

[JakeFeyen]

I thought it was the Transfer case motor at first, so i replaced it, and that didn't help anything. And there is no clicking when it doesn't work. we also tried taking the Transfer case motor off so that it had no restrictions (keeping it plugged in) and yet it was still random as far as when it would work and not work.

 

[aclasshog]

You could jack the front up and verify the hubs are pulling in, if not then it's most likely vacuum. If you can hear the motor pulling in on the transfer case then you need to start troubleshooting switch, fuse, wiring, plug.
Good luck

 

[Andrew Hubert]

even if the hubs are not pulling in the transfer case should lock in and the 4x4 light should come on.

 

[klhansen]

The way the system works is there are two relays under the hood next to the fuse box (should be in the small box in front.) Those relays get controlled by the GEM in response to the switch position on the dash. When one is energized, the motor shifts from 2WD to 4high and 4low, and when the other relay is energized the motor moves back the other way. There's also a feedback switch on the motor that tells the GEM what position the t-case is in that opens the relay when the position matches what the switch setting is. The hubs get locked by a signal from the GEM to the hub-lock solenoid mounted behind the passenger side battery. Going from 2WD to 4WD, the hubs get a long pulse of vacuum and going the other way, they get a short pulse (that may be backwards as I'm going from memory). If the problem is intermittent you could try changing out the relays, but I would more likely suspect a problem either with the dash switch or the feedback switch on the t-case motor.

 

[jeepwillys]

I agree with KL, if the relay is clicking or activating intermittently. Then it's from the transfer case to the switch. In other words, Indeed KL, Indeed.

 

[JakeFeyen]

sorry i should have said so at first, but the Vacuum system for my hubs has been either disabled or deleted, and they have manual locking hubs, i have to get out and lock in the hubs by hand. which they lock in just fine, and my front driveshaft spins, there is just no power. And its up stream from the Transfer case motor. My truck is currently in the shop getting other work done on it, so i have to wait to get it back to go further with it.