I have a 05 f150 stx. Recently I had to replace the rear u-joint, easnt thinking and didn't check transfer case fluid after putting the drive what back in. We have had a lot of snow today and went to use 4wd. In drive there is a whine in 4hi the whine get louder in 4 low. In reverse the transfer case seizes up after moving about 3 ft and stops completly then after pressing the gas a little harder mover again then seizes up again in 4 hi and low. Added transfer case fluid to fill back up thinking that was the problem but is dtill doing it.

 

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my 07 does that and I have not figured it out yet. GL will be watching this thread