odd clunking noise

[dudeguy]

hey guys,first post here but ive been browsing the forums for a couple months..so,i have a issue with 4x4 and wouldnt mind some suggestions to start looking.Im not very mechanically inclined so I dont know where to start.
In 2wd,the truck drives great until i hit the brakes with a little force,i suddenly get a clunking coming from the front that goes with every wheel rotation.it keeps clunking for.5-10kms then goes away randomly and comes back again when i hit the brakes.
Now in 4x4,that "clunking" is constant with every wheel roation from the time i engage 4x4 until i disengage it unlock the hubs and drive around in 2wd for a few minutes.
knowing very little about suspension or mechanics in general(I only learn how to fix things thanks to youtube lol) I cannot figure it out,ive tried to pinpoint the noise but that proves difficult as it only happens while moving.any suggestions on where to begin looking are appreciated,id like to fix it myself if at all possible.thanks guys
edit-its a 94 explorer all stock xlt btw

 

[leftoverture]

Really hard to give you input over the Internet without actually looking at the vehicle, but from your description I would start by checking the wheel bearings and front u-joints.