First time poster here. I'm a die-hard Chevy guy but am in charge of a fleet of Fords at work, so it's my first time working with solid front axles and locking hubs.

Our 2013 F-250 has a faulty 4x4 system. It has a switch to activate the rear locker (seems to work fine), and a manual shifter for the 4x4. When I put it in 4 high, there's a nasty knocking sound and hop from the front left axle\wheel. It increases with speed. It's so bad that I can't even test the 4x4 system in dirt or snow. It also happens with the hubs locked and unlocked. Where should I start to diagnose it past this?

Also- what's with the locking hubs? How do they work and what position should they be in when I'm in 2WD?

 

My 2012 F-250 4X4 has manual locking hubs. There are 2 positions. Manual and Auto. Mine stay in Auto. I assume without knowing the actual function that when in Auto and only 4x2 operation that the hubs "unlock" or free wheel. What you are describing sounds like an axle issue the best I can guess without actually being there and seeing the truck.

 

On a manual shift transfer case truck the hubs have a free and lock position. You can leave the hubs locked in all the time if you want but there will be a drop in mileage and more wear and tear from everything up front spinning all the time.

Don't know about the noise but if the hub is in the free position nothing should be spinning up front. I wonder if you have a problem with the unit bearing or something.

 

As fordman19762003 noted, you should normally keep the manual hubs in the "Free" position when you have the truck in 2WD. That will disconnect the entire front axle from the wheels and the transfer case lever will disconnect the front driveshaft from the rest of the drivetrain, allowing the front axle and driveshaft to avoid spinning unnecessarily when you are in 2WD. From what you are describing, it sounds like you may have an issue with the front axle u-joint on the left side. You should be able to see that u-joint without taking anything apart and you should be able to check it by hand for excessive movement. If the hubs have been left in the locked position all the time, those axle u-joints will have been spinning and getting wear, even when in 2WD.

 

Leaving the hubs locked doesn't put much extra wear on the u-joints Jeeps and Ram HDs have the front axle spinning all the time, I would be more worried about leaving the hubs unlocked for a long time and the u-joints seizing up due to not being used.

 

^^^^^ I'm of the same thinking on this.....I leave mine locked in all winter even though my ESOF works fine. I also lock them in every few weeks in the summer when going for a drive just to keep everything freed up.

I'd be suspecting/checking for a seized u-joint at left front wheel at this point.......Also have a look at u joints in front drive shaft......specifically the joint at the front differential, it's always getting sprayed with water and what ever other crap is on the roads.....this can also cause a vibration on the left side.

 

 

Got it going into the shop next week. The mechanic who test drove it thinks it's a wheel bearing going bad, or that locking hub on that side.