2002 F150 Front Diff Noise
 

Hello,
This is my first post on my First Ford Truck.
I just had all this work done because the front end was loose and vibrated over 50 mph: New control arm/ball joints, upper and lower, all new u joints and front end alignment. Afterwards the truck is definitely tighter and handles better but from the moment you start rolling there is a noise from the front end that sounds like I'm riding on some big off road tires which continues all the way to about 55 mph where the front end has the most vibration. You can't hear it outside by sticking your head out the window but you feel it right below your feet. So while it was up on a lift we spun the drivers front wheel and you can't hear it at the wheel but if someone is in the cab they can hear/feel it. So as someone was spinning the wheel we went underneath and traced it the the yoke of the front diff, you can put your hand on it and feel the vibration. There is play in the pinion as you turn the front drive shaft left and right, should this be tight?
What do you think this is, a bearing?

If the front diff isn't engaged/I'm in 2wd the front drive shaft shouldn't be spinning should it? It must be because that is where the noise is coming from. Can I stop it from spinning somehow? Duct tape?;)
At first I thought maybe they put the drive shafts in differently after replacing the u joints but that wouldn't cause the noise when your only going 0-5 mph and like I said this noise is there as soon as you start rolling. It wasn't there before the work was done but the vibration at 55 mph feels just like it did before. Sorry for the long winded post, just wanted to get all the info out right off the bat.
Thanks

the pinion should move maybe a 1/32 of an inch back and forth by hand. That is the few thousands clearance between the gear mesh inside. If your moving a 1/4 inch, or up and down or in and out movement, you have a problem.
Your 4 x 4 has two engagements. You engage an electric motor at the transfer case that pwers the drive shaft turning. Then you have two vacuum hoses and a vacuum cylinder that engage the front axle inside the pumpkin. You should just have the front drive sahft going along for the ride if the transer case motor is not engage. You should not feel the drive shaft at 5 MPH. Probably not even turning. You may have abearing problem at the axle shafts on the pumpin, if that is the area of the vibration.