Vibration in front hubs?

[bard@domain.elided]

Hi, 
    I was hoping for some advice on two things before I dig into my '77
Scout II. 

 1) When travelling down the road and passing over a bump, the front
end      develops an almost grinding vibration until I slow to about
5-MPH and then it goes away till the next good bump. I had a similar
problem on another Scout II I had and when I took it to a shop they had
said that apon inspection of the hub's they found a loose washer that
was rubbing the bearings and they just tightened it back up. Any
suggestions ?

 2) I will be replacing the transfer case on my scout soon and was
hoping for some advice before I get into it, it is a T-145 connected to
the 727 and a V-8 304. I hope this will not be too difficult as I do not
have a garage and the snow here is about 3 feet deep around the truck.

Thanks for your help.