Does this happen when you're at a dead stop, when rolling, or both? IF it's only when rolling, does it happen if you're coasting at speed in neutral? If so, try this: Find a hill and roll down it with the engine off, trans in neutral and foot off the clutch pedal. Let me know what happens.
There could be problems with the main shaft or the output shaft.
Sunday, October 9th, 2011 AT 1:12 AM