Couple hundred thousand miles and the carrier is bad, along with the rest of the suspension rubber.

I doubt the engine coversion did anything, the same part is used in the 6.9 and it has MUCH more power....

The thumping is the driveshaft "orbiting" instead of spinning on axis under acceleration, pretty common by your milage.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!