So I should learn to do my homework before making suggestions. I was checking out the design of the CVT and it doesn't use clutches, which means there are no solenoids that route fluid through ports. It is simply a pulley that changes in width causing the belt to ride up or down making the turn ratio change, thus making the wheel rotation speed go up or down.
I know that they started with the CVT on the Altima near the beginning of this century so you may want to check that forum to see if they have similar symptoms, assuming of course this ends up being CVT related.
I hope it is as simple as a drive shaft. But then again that means I may have this problem.
On a side note, I can fell a slight thump when changing from P to R to D or visa versa, but I have to assume it is normal since I am not familiar with the CVT. Mine only has 500 miles on it.
1996 200SX-SER (Taking a Vacation)
2010 Sentra SR (Making the 200SX Jealous)