What's this vibration?
 

I recently purchased a 94 GT convertible with the T5 transmission. Love the car but needs shocks and a tighter chassis (next spring project). Recommendations appreciated.

Anyway, I am getting a rattle/vibration at approximately 1000rpm. This only happens when the drivetrain is under load and it happens both when the clutch is being released (during start up leaving a light etc.) or is fully released (already in gear rpms drop below 1000 then move up to 1000). This is driving me crazy, I'm afraid damage is occurring and the "cool" factor goes way down when starting out with an audience due to the rattle. So far my solution has been to try to start out with rpms above 1000 but I'm looking for something a little more permanent. When I first bought the car I thought it was coming from the rear end and suspected the diff. Now it sounds like its originating from the transmission area but definitely under the car. Since I'm in the car I can't really isolate it.
Any Ideas?
Thanks

Friend of mine had the same problem. He has a 95 gt. Real bad vibration at about 1k rpms. The harmonic balancer went bad.