I have a 2012 F250 4x4 gas regular cab 120,000 miles. I have started noticing a noise coming from under the truck. Its a scrunching sound when the vehicle is moving. It sounds like a failing u joint. I put the truck in neutral and went under the truck and moved the drive shaft around. There is some slack in the differential but not too much. The u joints do not seem to have any noticeable wear. I grabbed the drive shaft at the transfer case and felt some slack in the yoke? Is it normal to have yoke movement or is the bearing going bad? The rubber boot on the drive shaft has a spline in it correct? Could this be making the noise? Any input would be appreciated!

 

there will be some slack in the slip yoke of the driveshaft. Make sure the front hubs are unlocked and see if the truck still makes the noise when you drive it. If it still makes it then I would bet something is bad in the rear. I had a u joint go bad once and it would squeak when I drove but it was still tight when I checked it. U joints won't always be loose when they are starting to fail. It's also normal to have some slack in the differential.