I am new to this forum and this is my first post so hopefully it's in the right spot.I recently bought a 2003 F350 super duty dually automatic transmission 6.0 deisel 4x4. The 4x4 is not working. with the hubs in auto when i flip the switch to 4x4 high nothing happens.The same with 4x4 low putting the truck in nuetrel. I can only find 2 fuses using the owners manual that says anything about 4x4 and both of them check out good. Also the owners manual says when i turn on the key I should see a 4x4 light and a low range light momentarly. Neither of these lights are showing up.I dont hear any clicking or any noise of any kind when trying the 4x4.It acts like an electrical issue but not sure where to start.Any suggestions would be greatly appreciated. Thanks Curtis

 

I would first try to manually lock the hubs, turn on 4x4, and check function. If it works when you manually lock your hubs, then you likely have a vacuum leak associated with the hubs. New o-rings and hoses would likely be in order. If it doesn't work even when you manually lock, then it is a problem higher up, and hopefully someone will be able to give you advice on where to start checking. But eliminate the hubs first. They are a known trouble spot.

 

Ok thank you I will check that

 

Ok I feel like a dummy the lights on the dash do show up but you actually have to start it not just turn the key on

 

Just to clarify my last statement the 4x4 still doesn't work just stating the lights on the dash do momentarly light up when you start the truck

 

OK. So you've established that the 4x4 indicators in the dash work. But when you switch to 4WD, the light does not come on. This means that the transfer case is not shifting and directs our attention away from the front hubs and to the transfer case.

Probably the first test to do is to get an assistant, get under the truck with a standard test light and find the 2 pin connector to the transfer case shift motor. Unplug that connector and connect the test light between the two pins of the connector. With the key in the RUN position (the engine doesn't actually have to be running), have your assistant turn the **** to 4WD. The test light should flash a number of times as the 4WD module tries to engage the shift motor.

IF the light flashes, then everything upstream of the shift motor is working. Inspect the connector, and the plug on the shift motor it connects to for any sort of corrosion or indication that there might be a bad connection. If everything looks good the shift motor is probably bad and needs replaced.

If the light does not flash then you need to find out why. The next most likely problem is one of the transfer case shift relays. The shift relays will be in a auxiliary relay box under the hood, drivers side towards the rear of the vehicle. They are usually in a relay box by themselves. Two identical relays with nothing else in the box. The box is wrapped from the factory with fabric electrical tape, but that might be gone if someone has already opened it. First thing to do is remove the relays and look for corrosion. If you find corrosion, clean it up good and try again. If that doesn't work, continue to the next step.

A good test of the relays is two remove them and swap their positions. One of the relays is used to turn the shift motor from the 2WD position, to the 4WD position, and then to the 4Low position. The other relay turns the motor back the opposite direction, from 4Low, back to 4WD, then back to 2WD.

When the relays are swapped, try shifting into 4WD again. If it works, you've found a bad relay and should probably just change them both.

If none of this works, then we'll need to look at the relay base wiring for corrosion and possibly move on to the 4WD control module.

 

DC. Thank you very much for the information I am anxious to try your suggestions I am not used to the electric shift 4x4 stuff had lots of 4x4's over the years but they have all been manual shift. I am away from the house for a few days but will report what I find later. Thanks again

 

Hey I have a 2003 Ford F-350 6.0 it's srw lariat edition it has Manual hubs but electronic 4x4 switch I have changed all fuses and relays but still the light won't come on I've tried manually locking the hubs and still nothing would be very thankful if somebody could help