Howard Stern Wack Pack Member Big Black Dead at 64

Big Black -- one of Howard Stern's famous Wack Packers -- is dead ... TMZ has learned.

The NYC Medical Examiner's Office tells TMZ ... Big Black died of arteriosclerotic cardiovascular disease, a condition in which fatty plaque builds up inside the artery walls, causing them to narrow and harden.

The M.E.'s office declined to say where or when he died, but the condition is considered a natural cause of death.

Big Black -- whose real name was Ronnie Benjamin -- appeared on the Howard Stern show back in the day with fellow Wack Packer Lawrence Coward -- who Howard called the "King of All Blacks."

Although Big Black was not a regular on the show, Howard would keep him for extended interviews when he was in the studio because of his brutal honesty about his bleak existence, which fascinated the Shock Jock and his audience.

In fact, almost everyone who listened to Big Black's Q&A's with Howard and his sidekick, Robin Quivers, fell in love with the Bronx-born man, who was also smart and well-spoken.

Big Black attended the elite Bronx Science High School and was a member of Mensa, but he ended up on public assistance.  

He was known for Howard's probing questions about his sex life ... and for his on-air dynamic with Robin.

Big Black was 64.