Erik,
Have you checked to see if there's play in any of the control surfaces?  I seem to recall some folks having lash in the elevator after a certain amount of flight time.  If the elevators are balanced they shouldn't go divergent, but may move if there's play.  They could be driven by fuselage-transmitted engine/prop vibes or aerodynamics (either unsteady prop wake or a bit of flutter).  Any slight slop in the hinges would then progressively get larger, and vibrations would get worse.

Without knowing the cause, driving is probably a good choice...

 Cheers,
- Kyrilian


asw20747@aol.com wrote:

*  At 165kts and greater, on three successive flights, we felt a distinct cyclical type vibration setting up.  It's a bit hard to describe in words but it does NOT seem to be a steady              vibration (like a gear door) but seems to feel almost like a prop out of balance.
*  Without touching the power or prop we can make the vibration go away by raising the nose and slowing < 165kts.
*  When we do get the vibration > 165kts..... you can mitigate it somewhat by increasing prop RPM.  The vibration is still there but not has bad.

<snip>

*  The issue is serious enough, in my mind, that I am DRIVING tomorrow from San Diego to Las Vegas.......and I HATE driving;)))

---

Be a better Globetrotter. Get better travel answers from someone who knows.
Yahoo! Answers - Check it out.