So iv been having issues with my 2014 F150 4x4 system. when in 2x4 she runs normal but when I switch to 4x4 the front drivetrain makes a noise like metal being shaved from a lathe but only on deceleration higher than around 45MPH. I have an appointment with my local Ford dealer as I'm still covered under Powertrain warranty. but this will be their 2nd time trying to fix this issue. Any advice on what to do if they cant/wont fix it? I checked the front diff oil level and topped it off taking almost half a quart. I also shook all the drivetrain parts to see if anything was loose and nothing. After the first time the dealer said it was normal case wind up noise or something like that but I don't believe them seeing as I still have a issue with it.

 

Yes. If the dealer can't/won't fix it, stop back here.
No sense going through the problem here if your going to have the dealer fix it.

 

just to head you in the right direction, the differential is not the problem.. There are vacuum pistons at each wheel end that engage and disengage the front wheels. When you take your foot off the gas, or stomp on it, the VACUUM changes... That can make the wheels party disengage... possibly you have sticking on the wheel ends vacuum area.... possibly you have a vacuum leak.

 

It lost a half quart while still being under warranty?

I say it that way because it should be able to hold all of its gear oil in for 100,000 miles or more.

Take it back, and if they give you the "normal case wind up noise" baloney again, request they show you another truck like yours that does this.

If they can't fix it, find another dealer.