when i refilled the transfer case I am hearing a whistle noise is that normal?

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my transfer case was not going into gears right with my 4x4 gm sierra 2500 1999 model. i refilled it with the transfer oil. but i am hearing a whistle noise, it is shifting now and not jumping like the emergency brake is on..do you know what the whistle noise could be???? I am stuck in the mountains needing to go back to ms. should i trust it???