2017 XLT Supercrew. 5.0. 3.73 gears. 4x4. 104,000 miles.

I started hearing a faint bearing whine a few months ago. Typically heard when slowing from 25 mph. It started getting worse over the last few weeks and can now be heard when cruising at 40. Coasting or light on the throttle. Only seems to happen, or at least becomes audible, after the truck has been warmed up to operating temperature. Kind of sounds like the whine from off road tires (I have highway tires). Just before coming to a stop is becomes a clear metal on metal grinding (this just happened most recently).

It's not the brakes. Pads and rotors on all four corners are still fairly new and in good condition. Not worn, warped, or rattling.

I thought it might be the driver's side front wheel bearing, so I replaced that and the IWE. No change. I have the parts for the passenger side and will do that in the next week or so, but don't believe they are the issue.

I tested the entire IWE system and it all checks out. Getting 24" of vacuum from the engine. The check valve, solenoid, and reservoir check out good. The lines and IWEs hold vacuum, no leaks. The sound is there in 2H or 4H, no difference. I unplugged the vacuum line at the solenoid, no difference.

I've read a bunch of threads about front diffs going bad, so I checked the fluid. Definitely has some metal flake in it. But here is where I'm stumped. My truck is an XLT and does not have the 4A setting. Most of those threads are for Lariat and higher trims. Do the front driveshaft/diff/CV axles turn in 2H? I didn't think they did, but what could I be hearing? I changed the front and rear diff fluid at 93,000 miles and observed no metal at the time, but admittedly didn't look that closely because I wasn't having any issues.

Anyway, it looks like a rebuild or salvage yard diff is in my future. Does the factory service manual cover this procedure? I'm a pretty capable shade tree mechanic and have most of the tools. I might buy a salvage diff and swap in new bearings to minimize downtime.

Thanks in advance.

 

Let me ask this: does the service manual cover transfer case and differential rebuild? Or should I look for another manual?

I've determined that the front shaft does not turn in 2H, so while the metal in there is a concern, its not what I'm hearing.

I've narrowed it down to something in the transfer case, very possibly the output shaft bearing. The bearing is readily available, but I can't find any videos or tutorials on changing it. It looks like the case needs to be split as there is no separate tail shaft.

 

The Ford Workshop Manual provides detailed rebuild procedures for both front and rear differentials and the transfer case.

Yes, the case needs to be split o remove the output shaft bearings and seals

 

Thank you! I don't mind spending the money for one, but didn't know if it covered more than r&r of these assemblies.