The best way to diagnose your problem is to crawl under the car and inspect everything. The driveshaft support bearing, and flex discs would be my first thought, but you should also check the axle boots and joints.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth