'02 expedition int. 4x4 disengagment

[UBET]

hey, i know its not a diesel but got a '02 expedition with and int. 4x4 dis engagment a4wd

while driving in 4x4 hi will clunk into at steady speeds 80km/h...changed motor,gem module, chain/gears...removed rear shaft and drove monitior pids front/rear speed whemn concern happens front speed but rear flares and no go

please help thanks

[Torqued_Up]

Are you saying that this transfer case is SHIFTING out of 4X4 on its own? The only clunking concerns I have run across were malfunctioning auto hubs usually caused by vacuum leaks at the axle seals... or a destroyed hub.