3 weeks after I got my H3 w 82k miles the check engine light comes on and gives codes for transmission proble. Still under 30 warranty from carmax so they take it to MrTransmission and put a rebuilt one in w 12,000/12 mo warr. Everybody's happy, happy, happy.
Last night coming in to the subdivision down a hill it shifted so hard I thought I was rear ended. WTF??
Didn't do it this morning on way to work but very skiddish now. I'm taking it in sometime this week for them to look at it. But, damn what could it be? Not even a 1000 miles on this one yet.

 

Check the transfer case fluid... if it has a bunch of metal shavings in it... then that is not good obviously. Some guys recommend changing the transfer case fluid ever 25k-30k miles to be on the safe side. The previous owners may have neglicected to change it at all.

Take it back to carmax or MrTransmission... I believe there is a difference between remanufactured and rebuilt. One may be better than the other.