Hey guys, I've got a 94 F-150 4x4 5.0. It's got manual hubs and it's an automatic trans with the push button 4x4 selector switches on the dash. My question is this: recently, I've noticed a strange squeal coming from the front drive train, but only if I have the hubs locked in. It doesn't matter if it's in 4 wheel drive or not. It starts at about 30 mph and doesn't go away until slowed to about 20ish. I havn't noticed any unusual leaks from the front differential, only some minor weeping. I checked the gear oil in the front diff and it is serviced properly also. Any one else have the problem, any ideas.

Thanks