Drive Train Axles Bearings problem
1988 BMW 325 6 cyl Two Wheel Drive Automatic 100000 miles
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there is loud pounding from underneath the car when i first take off then it goes away at about 15 to 20 miles per hour

The center support bearing for the drive shaft has lost the webbing that holds the shaft in support and will require repair or replacement of the entire drive shaft. The age and mileage of the car might indicate that replacement is in order. There are several drive shaft re builders that can send this item to you UPS or Fed-ex. Let your fingers do the walking as they say.