I have a 2015 F150 FX4 with the 4A. The transfer case seems to always be engaged, even when in 2H. I had a loud bearing noise start in the front end. I changed both front wheel bearings and checked the actuators. Noise was still there and getting louder. Come to find out, it’s the front differential. Bearings are shot. I didn’t think I should be hearing this in 2H. I thought everything would be disconnected in 2H. I jacked the front of the truck up with it idling and verified that the hubs are unlocked, the CV axles don’t turn when the wheels are spun. Then I jacked up the rear and had someone put it in gear. The front driveshaft, front Diff, and CV axles are turning in 2H. It seems the transfer case stays engaged and only the hubs unlock when in 2H. Is this correct, or is there a problem with the transfer case or shift motor?

 

Sounds like it's stuck in 4wd. Even if it is in 4A you're technically 2wd until it needs 4wd for traction.

 

The front driveshaft on your Lariat or above will rotate a little regardless of 4x4 position. Just the nature of the type of transfer case. The front drive shaft rotation speed should not be equal to that of the rear -there is just a slight amount of drag, enough to twist the driveshaft.

Front diff bearings are too common on these vehicles.


I, and others, have witnessed the front drive line rotating while in motion and in 2wd. I have not put 4 wheels in the air to check though. I had it up just one time, when I first purchased it (used) because I was going to the snow a week later and wanted confirmation 4x4 was functional. Never raised the wheels in any of my inspection for noises similar to what you probably experience.

 

Yes, 4A (torque on demand) transfer case has clutch drag that will keep the front rotating.

You can find a used front diff from a XL or XLT (so the front does not turn while in 2wd) on car-part.com for around $400-600.