My left front locking hub on 4x4 ford truck wont lock in

Check your hubs lift front end if wheel does not turn when locked in 4x4 then hubs are not engaging turn wheel by hand or a pipe wrench on drive shaft do not try power unless all wheels are lifted

ok does noise change when turning left or right if not its not a wheel bearing next try putting in neutral at 55 does noise change what you are looking for these is pinion and carrier bearings in differential the noise can be coming from several places have you checked all your fluid levels front and rear diffs and transfer case also check fluid condition also check for metal in fluids if you stick finger or paper towel in and if you see metal you will know where your noise is coming from

replace locking hubs

Before you start the vehicle lock the hubs in by turning the lock out device in the hub center of each front hub. Now you can start the vehicle and while in park or neutral move the range selector on the floor to the range you would like to use. Most often you will use the 4 wheel high setting. The low setting is only for extremely heavy pulling and will throw you across the seat if you accelerate too hard. Never exceed 45 miles per hour when in 4 wheel drive as you will burn out the transmission or 4X4 transfercase bearings. Now to go back to two wheel drive. Move the floor selecter back to 2 wheel drive setting. Do this with the vehicle in park or neutral to prevent damage to the vehicle. Now you can unlock the hubs by reversing the hub lock out device in the center of the two front hubs. Important little known fact is that you do not want to drive aroind with the hubs constantly locked in as you will lower your fuel mileage and cause extra wear to the axles and associated parts. Hope that helps, please come see us again if you have any more questions, Thanks, Rich.

A howl usually is a bad bearing

Are you under warranty? Make it the dealers problem if its eligible.

If the front hubs are grinding regardless of being in 2wheel or 4wheel drive it can be the hub bearings which turn regardless. If it grinds only when in 4x4 then the wheel shafts or differential or front driveshaft or transfer case is making the noise because all of these parts move when in 4wheel drive.

i would bet you need to replace your locking hubs

Check the front wheel bearings for play and also while the wheel is off the ground lock the front hubs, grab the axle behind the wheel and see if it is engaged. If not then you will need to take the hub apart and find out what is broken.

check the vacuum lines going to the hubs and make sure the hubs are locked in

check wheel bearings and axle joint at the end of the hub