Loud clunk/rattle while in 4x4 need help asap!

[Dancin'Arrows]

Got a issue that just came to my attention with the recent snow falls. When I lock my hubs in and attempt to drive in 4wd, i get a loud clunk, clunk, clunk, clunk etc. that increases in rate with speed. The front end was torn apart this summer to replace the spindle bearings and drivers side axle shaft. The truck drives down the road in 2wd just fine with no issues what so ever. And even though there is the clunking, the truck is in 4wd, as it had to drive itself out of a ditch not long ago. I am keeping it in 2wd until I can figure out what is going on from fear of causing some serious damage, but with more snow on the way, driving can become a pain. The truck is a 2000 f350 srw. Any help or suggestions will be a big help, I haven't had time to tear anything apart yet due to work, so looking for a starting point.

[Jordan72]

i have this same problem and my dads truck is torn appart right now for the exact same thing. we figured it was something in the front axle because when we disconected the front driveshaft the clunking went away... but after going through the front end and finding nothing major we figured maybe it was something in the transfer case when it had load on it.

Have you found out anything about yours?