General 4th gen 4WD question

[37ford]

In normal 2wd operation, are the front CV joints supposed to be disengaged from the hubs?

Is the ITW a system that uses vacuum to disengages the CV and hub in 2wd?

If I am inspecting the front suspension on jack stands, do I have to have the vehicle running to spin the hubs without turning the CV joints as well?

 

[BMW2FORD]

Yep, Ford calls them IWE’s and in 2wd vacuum is sent to the front hubs to disengage the axles. If you have it on Jack stands, look at the back of the hub and you’ll see a fat vacuum line that looks like it’s has two hoses in it. The large is the vacuum sent to it from a plastic vacuum reserve tank on the firewall above the master cylinder. The small line is just to vent the IWE. I had seen your other post and thought best to do is drive in 4wd and see if the noise goes away. A lot of times, the check valve between the vacuum tank and engine goes bad so the tank doesn’t hold enough vacuum in 2wd applied to the IWE so it sort of engages and partially disengages and you get a grinding noise. I like to use a hand held vacuum pump tester and apply straight vacuum right to the large line on the IWE at the hub and see if it holds vacuum and while it does that the axle spins. That will help tell if the IWE is OK. Ford did have and still does have a lot of problems with that check valve. Just Google IWE check valve and tons of info and pics will come up. One word of caution in case you try to use the engines vacuum on jack stands to test - after a start up, even if the button is in 2wd, sometimes the system will keep the fronts in 4wd and hold off applying vacuum although the interior button is lit up as 2wd until it sees the vehicle driven. Ford built a few algorithms into the vacuum strategy after start up to be sure enough is present before applying. This usually happens in cold weather.

 

[mreed112]

IWE's have been deleted on 22+ 4WD with 2 speed transfer case.

 

[37ford]

I mounted my borescope to look at the CV axle and took it down the road. The CV axles. Of course, the CV axles turn full time in 2H. I checked the IWE valve with the car running. There was vacuum coming into the valve, but none coming out.

I put vacuum on the line going to the hubs, and it held pretty steady. So, I ordered a $20 valve. I hope that’s all there is to it.

Seems like you could just bypass the valve if you don’t intend to use 4WD.

 

[JExpedition07]

So Ford has changed the way the IWE works, the ones that still get IWE now use an electric IWE, but it still utilizes vacuum as well. Then 2-speed auto transfer cases get no IWE. My 2023 F-150 has ESOF (2H, 4H, 4L) and I have the electric IWE’s on my CV shafts. Then again the F-150 does not offer a non 2-speed transfer case, they are all 2-speed but some upper trims have an auto mode like the expy. The ones with auto do not have IWE’s on the F-150.

Depending on your year (18-21) are the same as a 2005 in the way they function. Ignition on in 2WD the CV shafts should not spin, then in 4WD they should when you spin the wheel. If you have an 18-21 there will be a solenoid that controls and releases vacuum to the hub diaphragms.