Trans rattle in low speed

[matrophy]

Replaced rebuilt 5 speed including new clutch, TO bearing and new stock-weight flywheel and I now have a rattle at low speed in first gear like when creeping up to a stop sign after stopping short of the line. It goes away once I accelerate.

 

  Could this be the new clutch breaking in or something wrong inside trans or with the clutch? Maybe the old girl doesn’t yet know how to act with new parts.

 

From searching I understand that it may be something external rattling but it sure sounds like it’s in the drivetrain. I had the exhaust and heat shields disconnected and I’m reasonably certain that they are fastened down like they should be. 

[datzenmike]

Have someone pull away while you kneel down beside the car, Try both sides. Back it up on blocks or straddle a ditch, climb under and shake the muffler and pipe. Try to hit something with it.  It may be a loose hanger or clamp.