marinemike0931

Oh and I also remember you saying that WOT reduces the amount of vaccume... so I thought it would be relevant to say that the the issue is more easily replicated at WOT and/or under heavy acceleration (it takes little to no bump to have the whinning noise engage).

bjohns7778

The issue you are having sounds a lot like what my '10 w/ 45,000 miles is doing. The first dealership I had it to replaced the wheel bearing to no effect, then replaced the IWE which seemed to fix the problem for 4 or 5 days. I took it back a third time and they adjusted the park brake cable(!?!) also to no effect. I took it to another dealership last night. Will let you know what they say when I hear from them.

VTX1800N1

That does lean more towards a vacuum problem in the 4x4 system. Vacuum @ the IWEs should be equal. You also need to test the reservoir and all the check valves. Those check valves might be in a different place or number from my generation truck.

Northofleduc

I have an 09 XLT SCAB 4x4 that made the grinding noise. I new right off that the hubs were trying to engage. My 95 SCAB did the same thing with the early version of automatic hubs. Took it to my dealer under warranty. Their diagnosis said both IWE's were weak and replaced under warrany. As far as I am concerned, any vaccum operated device that can't hold vaccum is broke!!

After the IWE's were replaced, I noticed an immediate marked improvment in performance and milage. Must have been engaged a lot or the vaccum imbalance threw the engine vaccum out of wack too.

Thanks for the explanation on how the system works. When mines off warranty, I'll at least have the procedure to check the system before buying parts that wouldn't be necessary.

Bcook454

My 2004 FX4 will not engage in either 4H or 4L. When switched to 4H all I hear is an electrical click. When switched to 4L, I hear a click and a clunk like it locks in, but it doesn't. I replaced the IWE solenoid after reading some other posts, but it still won't engage.

After doing a little more research I decided to check the system by turning the driveshaft while 4x4 is engaged and this is where I am now confused. With the truck running in 2H, I can turn the driveshaft by hand. When switching to either 4H or 4L, the driveshaft cannot be moved telling me that the transfer case has locked it in. However with the truck off, I can turn the driveshaft by hand. When the truck is off, shouldn't the vacuum be released therefore locking in the IWE's? I am trying to diagnose my issue but this has really confused me. Can someone please give me some guidance based on this info? Thanks in advance.

VTX1800N1

Yes, it should, and with both front wheels on the ground you should not be able to turn the front drive shaft with the engine off. Follow the diagnostic steps on page 1 of this thread. You have a bad IWE, hub, or both.

Bcook454

Thanks for the response. I figured that the actuators were good since it is apparently holding vacuum while in 2H. Is it just holding vacuum the whole time and never venting? I will follow the troubleshooting on the first page this weekend by lifting one wheel at a time and spinning them and putting a vacuum pump on the actuator.

VTX1800N1

No, the solenoid should vent the IWE side to atmosphere when the engine is off. The IWEs can fail disengaged or the IWE and/or hub gears could be ground up enough to prevent engagement.

Bcook454

So, I can basically rule out the IWE solenoid since that was changed out a couple weeks ago. The IWE actuator is either stuck in the disengaged position or the gears are worn. Where can I check to see if the solenoid is venting?

VTX1800N1

Attach a vacuum pump to the large hose @ the IWE.