So, a couple of weeks ago me and a buddy drove straight through from colorado to iowa and back to colorado to get a trailer about 27 hours of straight driving at least 10 or 12 of those hours through pretty much a blizzard and unplowed roads. We had the hubs locked in and were switching from two wheel drive to 4 high quite often due to all the snow. Eventually in the middle of Iowa in a blizzard the truck just wouldn't switch into 4x4 anymore. I'll turn the switch on the dash to 4x4 high and nothing happens, no light on the dash turns on, no enguagment of the front wheels. The same happens if I go to neutral and try to out it in 4x4 low. I started looking for power through the system and it seemed like the transfercase motor had died, they're cheap enough so I put on a new one on but still no 4x4 at all. What do you guys think this could be? What other diagnosis should I do? I'll definitely be looking into the switch on the dash but what else? All fuses and relays are good as well, checked at least 6 times by now lol

 

When you put it in 4x4 low does the heat go straight to defrost? If so you might have a vacuum leak.

 

Check the other bigger plug down on the transfer case. It is the encoder plug so the truck knows what mode it is in (2hi, 4hi, 4lo). If something is wrong with that plug or the wiring the truck won't shift the transfer case because it is a safety deal I'm thinking. I have had it happen twice on my 01, the first time one of the wires rotted through. The second time my repair fell apart and I had to fix that.

As a side note, the transfer case should still shift and indicator lights still light even if you have a vacuum leak to the hubs.


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In my case it was the 4x4 solenoid that is mounted in the engine compartment. It went out at just over 100k. Replaced it (5 minutes) with another OEM unit for $75 and all was fixed.