4X4 not working
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Joined: Nov 2006
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4X4 not working
Hey everyone, I have a issue. Hoping someone can shed some light. I have a '02 f250 SD 4x4 V10 Crew Cab, shift on the fly 4x4. I went to shift into 4HI a couple of days ago and nothing happened. The light did not come on and I did not hear it engage. Any ideas.
Senior User
Joined: Apr 2010
Posts: 345
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From: Taxachusetts
start with the hubs they are a known weak spot. They may need to be lubricated. Check here Welcome to guzzle's 4x4 Autolock Hub Lubrication Maintenance Web Page
Also check the vacuum lines that go to the hubs, they may have deteriorated or became disconnected.
Also check the vacuum lines that go to the hubs, they may have deteriorated or became disconnected.
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Joined: Sep 2007
Posts: 8,180
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From: Scio, OR
If your 4x4 light did not come on, then the transfer case did not shift into 4WD. The computer will not attempt to lock the hubs until the transfer case shift is complete.
The first test I would do would be to get a test light and crawl under the truck. Unplug the 2 wire connector attached to the transfer case shift motor. Attach the test light between the two pins of the connector. Have an assistant shift to 4x4 (key has to be in the RUN position but the engine doesn't need to be running). You should see the test light flash 3 or more times.
If it does, then the shift motor is getting power and has likely failed.
If it doesn't, then the next most likely problem is the shift motor relays. They are in a relay box on the drivers side of the truck near the brake master cylinder. They are two identical relays in a box with no other relays. The box is often wrapped with black fabric electrical tape. Check first for corrosion around the relay contacts and the connections to the box.
One of these two relays is activated to shift the transfer case from 2WD to 4WD, then again to go from 4WD to 4LO. The other relay is activated to reverse the shift motor back to 4WD, then 2WD. An easy test is to swap the relay positions. If the "shift in" relay has failed and you move the "shift out" relay into it's position, it will shift into 4WD and then not want to shift out. At this point, I would just replace both relays. They are relatively inexpensive from Ford.
If none of this works, there is more to test but it starts getting more complicated.
The first test I would do would be to get a test light and crawl under the truck. Unplug the 2 wire connector attached to the transfer case shift motor. Attach the test light between the two pins of the connector. Have an assistant shift to 4x4 (key has to be in the RUN position but the engine doesn't need to be running). You should see the test light flash 3 or more times.
If it does, then the shift motor is getting power and has likely failed.
If it doesn't, then the next most likely problem is the shift motor relays. They are in a relay box on the drivers side of the truck near the brake master cylinder. They are two identical relays in a box with no other relays. The box is often wrapped with black fabric electrical tape. Check first for corrosion around the relay contacts and the connections to the box.
One of these two relays is activated to shift the transfer case from 2WD to 4WD, then again to go from 4WD to 4LO. The other relay is activated to reverse the shift motor back to 4WD, then 2WD. An easy test is to swap the relay positions. If the "shift in" relay has failed and you move the "shift out" relay into it's position, it will shift into 4WD and then not want to shift out. At this point, I would just replace both relays. They are relatively inexpensive from Ford.
If none of this works, there is more to test but it starts getting more complicated.
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