You will change the characteristics of the lens and no longer be able to
focus to infinity.  Perfect for macro.

Rita

Don't forget the issue of the "extra mount tab" on the TC's which prevent
mounting a "normal" Nikkor (not AF-S) until the smaller "extra tab" is
ground off the mount.
Beyond that, using a extension tube with the TC should have the same effect
as using the extension tube by itself on the lens (closer focus, loose
infinity focus, etc) without the extra magnification of the TC and its own
exposure & IQ effects.
With Nikon extension tubes, you would also loose any electrical continuity
with the lens, such as autofocus with an AF-S lens (which the AF-S TC
maintain.
Bob

Those AF-S teleconverters are optimized for longer focal lengths so it
may not work well for shorter lenses. I believe the way extension tubes
effect exposure is that they increase the focal length so the aperture
becomes smaller relative to the focal length and the f/stop becomes a
larger number. a 50mm f/1.8 has an aperture diameter of 50/1.8=27.7mm
and if you add 50mm of extension it's a 100mm lens with an f/stop of
100/27.7= f/3.6

Also, you may have to grind off a metal tab on the teleconverter because
they are designed not to mount to some things. That modification has no
effect on performance. I did this in order to be able to stack my 1.4 &
2x teleconverters.

Oh, and I'm unable to mount my ancient pre-Ai E2 14mm extension tube to
the front of my AF-S teleconverters, only to the back. It starts
mounting but won't tighten & snap all the way. This may not be true for
newer tubes. I can do it but it's not secure and obviously there is no
aperture or AF connection (but this tube doesn't have that anyways).