well, as minne said, the rod wouldn't transfer energy perfectly, and would be subject to compression and damping of course...
however, i've heard that two subatomic particles linked in counter rotation will realign themselves instantly if one changes direction, no matter distance. i have no idea if it's true or not (i doubt it) and i'm too lazy to check at the moment.
but if it is, you could send binary messages faster than the speed of light.