2001 4X4 Clunk
 

Last winter my now ex-wife decided to drive the montero sport for 45 minutes while partially in 4H. The next day I went to drive it to the store, saw what was going on, and it not only would it not engage it just clunks really hard like a bad u-joint. It's not the u-joint, I checked. Since then I have not had the time, money or motivation to tackle it.

Now it's snowing again and I came for some advice, maybe on what to check first, etc...any help would be fantastic. Thanks everyone!