I've heard and felt a clunk 3 times over two days

[16plati]

I was watching some videos and maybe this is the problem. I bought the car back in 3/18. I pretty much only had it on 4wa until last week when I switched it to 2wd. Then a few days later the problems started.

No reason to have it in 4A should be in 2H while driving on pavement

 

[oldpaddy]

No reason to have it in 4A should be in 2H while driving on pavement

We get a lot of rain in the spring and fall and a ice during the winter. And I live on a dirt road. That's why I usually have it on 4wda.

 

[16plati]

We get a lot of rain in the spring and fall and a ice during the winter. And I live on a dirt road. That's why I usually have it on 4wda.

Do you exercise the other 2/4WD options regularly? I just had both IWEs replaced on my 2016 for grinding while driving. Vacuum lines, actuators, hubs and seals, check valves and solenoids

 

[oldpaddy]

Do you exercise the other 2/4WD options regularly? I just had both IWEs replaced on my 2016 for grinding while driving. Vacuum lines, actuators, hubs and seals, check valves and solenoids

Rarely. I haven't gotten a beach driving sticker for this expy, so I only use 4wd when my road hasn't been plowed, or poorly plowed, after a snow storm.

 

[Sgt Darkness]

Probably time for a good mechanic or the dealer to look at it. U joints can also make the clunking sound but they are relatively new so I would say no on that. If you find a fix let us know what it was....thanks.

 

[Mubarakma]

The truck is now a few years old, the vacuum hubs are probably losing vacuum and half engaging on the fly and will produce hard loud clunking. Almost feel like you are running something over when it happens in front?

It’s likely a leaky hub actuator seal or the solenoid on the firewall. Common issue of ford half tons.

Same thing happen to my car I have loud clunking and you can feel it it's near by gear shifter I went with a mechanic for test drive when he remove vacuum hose for engage and dis-engage 4WD and problem disappear he said if you need 4WD then you need to change vacuum hub other wise you can use your car as 2 wheels only .

 

[oldpaddy]

I switched back to 4a last week and the problem stopped

 

[Dustin Gebhardt]

Sounds like a vacuum issue. In 2H mode, the IWE's see vacuum, and keep the IWE's disengaged. If a drop in the vacuum occurs, then the IWE's try to engage. In 4A mode, the IWE's are without vacuum and should be engaged. The Expy's traction system monitors the various wheel speeds and switches on the transfer case as needed (along with applying the brakes to spinning wheels as needed and/or limiting engine power output).

Alternatively, the u-joints could be making the noise. My old 2001 Expy made a lot of clunking noises until I replaced all 4 u-joints (3 different sizes, BTW. Thanks Ford Engineers!).