02 pathfinder LE 4wd doesn't engage when cold

[2002pathle]

I have a 02 LE that the 4wd or auto 4wd doesn't engage when cold,below 30 degrees. It makes it a pain and unsafe in the snow. In order to get it to engage when cold, I have to just sit there with the wheels spinning trying to get traction, then all of a sudden I hear a bang, and off I go in 4wd or auto 4wd. Leaving it in 4wd overnight, makes no difference the next day if its cold, still no 4wd. If left overnight in a heated garage, no problem, the 4wd works from the get go. If its an easy fix, I can do it, if it isn't (expensive)I guess I'll have to live with it. Thanks!

[Towncivilian]

Drain and fill the transfer case to begin with. Use a synthetic automatic transmission fluid such as Mobil 1 ATF to improve cold weather performance. The part time transfer case takes 2.32 quarts of fluid.

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