I have a head scratcher. My 2017 XLT 5.0 will make a griding sound coming from the front end while in 5-6th gear 50-60mph. It doesn't happen while its cold only when its warm out. It generally happens while going up hills and accelerating to maintain speed. The second you let off the throttle it stops. I thought it was the IWE so I replaced the check valve and solenoid. Noise is still present. I disconnected power to the solenoid and drove it like that for a couple of days trying to make it do it and it won't make the sound. I took it to a shop and explained the issue and what I had done to trouble shoot it. They looked it over checked the IWE and said it was fine and was the transfer case. They drained it and found a bunch of metal in the fluid and replaced the fluid and said I need a new one. To me I find hard to believe that's the source of the sound since from my understanding the transfer case shouldn't be spinning while in 2WD. Is it possible its the Transfer Case?

 

If leaving your IWEs engaged (disconnected power) and the sound went away, to me, that's the issue. The solenoid and checkvalve are the simple cross my finger fixes. Personally I'd delete the iwes, or unplug the solenoid and drive on.

 

It drives ok around town but on the highway it feels terrible. It has alot of NVH.

 

Even in 2WD the transfer case rotates. The TC main shaft is connected directly to the output shaft of the transmission. In 2WD the only output is to the rear wheels, but any time the truck is moving, the transfer case has rotating parts. The higher the vehicle speed, the faster those rotating parts spin.

 

What would be symptoms of a failing transfer case?

 

Some symptoms would be:

• NVH emanating from the TC area.
• Metal shavings or chucks retieved during a fluid change.
• Leaking output seals.
• Excessive output shaft play or endplay.
• Failure of the TC to power front or rear axle.

I'm sure there are some others depending on the type and seriousness of the failure.

 

Just an update. I took my truck to another shop. They took it for a test drive and were able to replicate the issue. Vacuum tested the whole system and then smoke tested it. All of the lines were fine but it was leaking from the hubs itself. They also saw that where the vacuum line goes into the hub was swollen from the oil undercoating I've had done. They replaced both front hubs and the vacuum lines right after the hub.

 

Yup, rust proofing will impact the rubber vacuum hose. I have that too. Sounds like you found root cause.

 

Swollen vacuum hose fix is as easy as a plastic zip time around the swollen area on the fitting.

 

Who'd a thunk that. Interesting, another tool in my box. Thanks for getting back here and letting us know.