Ashurst made 409 appearances for the Black Cats - a club record for an outfield player - before moving into management.
He led Newport to the European Cup Winners' Cup quarter-finals in 1981 and eventually returned to Sunderland, whom he took to the 1985 League Cup final.
Ashurst's former clubs led the tributes, with Sunderland announcing they will hold a minute's applause prior to Saturday's match against Bolton.
Former goalkeeper Jim Montgomery, the only Sunderland player to surpass Ashurst's playing record, told the club's official website: "As a player, Lennie would have kicked his granny because he was a winner."
Newport tweeted: "Newport County AFC is saddened to learn of the passing of former manager Len Ashurst.
"Our thoughts are with Len's family and friends at this difficult time."
Ashurst ended his playing career at Hartlepool, whom he also later managed, and also had managerial spells at Gillingham, Sheffield Wednesday and Cardiff.
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