Need to understand what part of the drivetrain stops turning when I shift the hubs from locked to unlocked.

Reason is that with dash 4WD selector off and hubs in locked position I get a vibration - something like an out of balance tire. When I switch the hubs to the unlocked position the vibration goes away. So, I'm trying to understand where my problem might be - out of balance front DS, front axle, etc. but I need to know what stops turning when I unlock the hubs.

Thanks...

 

When you keep the dash in 2wd and lock the hubs, the axle shaft, axle U-joints and hub now turn. Some good reading here:

https://www.ford-trucks.com/forums/69...auto-hubs.html

https://www.ford-trucks.com/forums/83...auto-mode.html

Vibration could come from those axle U joints. How do they look and feel when you jack the front tire off the ground? Tight? loose? fresh rust at the edge of the cap?

 

I had the needle bearing in the hub going bad. Good reading on what to look for from links wpnaes posted. Good luck!

 

Not sure what I'm doing wrong but I can't access those links. When I click on them a message appears saying "The webpage cannot be found". Any suggestions?

 

yeah, linkies no workies.

 

Sorry about dat!

https://www.ford-trucks.com/forums/4...king-hubs.html

one more time...

 

Link works and out of the 9 page post, its post #18 that give a pretty good description.

In answer to my own question - with the dash switch in 2wd and the manual hubs locked the wheels, front axles and front driveshaft all are turning and the transfer case is disengaged. With the dash switch in 2WD and manual hubs unlocked only the wheels are turning, front axles and front driveshaft are not.

So, my vibration could be due to front driveshaft out of balance, front axles bent, or U-joints.

Thanks for the help...

 

Don't forget to look a the needle bearing that holds the axle shaft in the hub. If it is really bad, (dry) even with the hubs unlocked, it will grab the half stub shaft and make it spin. That was the source of my driveline shudder.

You can verify the problem when you pull the hub off. You will see damage to the axle stub shaft where the bearing rides.

Just one more thing to consider since the front axles are not known to bend unless your're rock crawling with your X. And the front drive shaft balance is not a common issue.