I have a '01 F150 Supercrew 4wd that has a problem somewhere in the front drive train. Recently, even with the 4wd disengaged, there is a loud howl when driving, similar to the sound of running studded snow tires.

I checked out the front hub/bearing assembly on both sides and they appear good. No slop or noise in them.

I noticed on the right side with the wheels raised and the brakes removed as I spin the wheel there is a high spot or point where the wheel hangs and I need to give it a significant push to keep it turning. It even torques the axle as it goes by this point. There also is some lash/slop in the axle too. The left side is smooth and rotates freely with no lash.

A few years back, the ball joint snapped on that side and the axle was ruined and was replaced.

My question is this most likely the axle/CV joints or could it be deeper into the differential?

Thanks in advance for any insight.

 

Check the brakes first.

 

I actually removed the caliper assembly and pads to get them out of the equation. I re-mounted the wheel without the brake assembly and spun it while it was off the ground. This is where I experience the binding, high spot or hump in the rotation. No grinding noise or clicking though, only the howling sound when it is driven.

 

I'd put my money on the bearings if it howls.

 

2001 F150 SC 4wd 103K miles
I wanted to provide some info in the hopes that this may help someone out in the future. I had a howl/drone in the front end. It turns out it was the passenger side hub assembly. In testing both sides I saw no play or slop on either side but decided to replace both hubs based on advice read in this forum. I did both sides to keep the wear levels consistent; the truck has 103K miles.
With the hubs off the truck you can feel the roughness when the passenger hub is spun. Something I could not detect when on the truck.
One issue I had was the hubs were essentially rusted onto the hubs, I tried PB Blaster, pounding, wheel puller, heat, nothing would work. I ended up removing the hubs with the rotors as one assembly. It was even difficult getting the hubs free from where they are press fit. A lot of rust in there. I don’t off road or go into water, just use the truck in the snow in the northeast. I guess time and miles take their toll.
The rotors needed replacement anyways. The inside surfaces on both were severely pitted. Almost like acid was dropped onto the surface and it stood there for a long time. Not typical score wear.
Regarding the binding feeling when spinning the passenger side wheel when raised. I don’t believe this is an issue. The differential is not centered, the passenger side axle/CV is longer. I had raised the truck under the frame cross member, both wheels in the air. The driver side has no binding, the passenger side does. I believe with the truck raised this way, the CV joints on the right are fully extended at a more severe angle. This is why it binds when spun. When I jack the truck under the normal jack point the passenger side does not bind when spun.
Lastly, I purchased the hubs and rotors from Advanced Auto Parts on-line with a local store pick up. Search the internet for on-line coupons; you can save a significant amount of money buying this way.