88 240DL, AT, 150K miles - Thump in rear. When starting from a dead stop hear a deep thump-thump-thump coming from the rear. The sound is only audible when first moving from a stand still and disappears at approximately 10mph. Usually comes in 2-3 thumps in a row but more recently have also heard 5-7 thumps on occasion. Sometimes the thumps happen 3 to 4 stop-and-go's in a row and then the next 3 or 4 starts from a dead stop no sound is heard at all. The best way to describe the sound is as if someone is hitting the rear end with a rubber 10 lbs. sledge or one of the tires is about to blow out.

Tires are ok. Also dropped drive shaft and manually inspected center bearing. Runs smooth. Checked the 3 u-joints on the shaft too. U-joints have full motion range without any binding or play. No bowling balls rolling around in trunk either. ;-)

Any suggestions?