The ranks of legendary Australian rock giants AC/DC are thinning by the day. After founding guitarist Malcolm Young left in 2014 following a dementia diagnosis, drummer Phil Rudd split due to some legal difficulties and singer Brian Johnson had to step aside this year because of a battle with catastrophic hearing loss, longtime bassist Cliff Williams has announced that he’s retiring. Williams, 66, who joined the band in 1978, said, “It’s been what I’ve known for the past 40 years, but after this tour I’m backing off of touring and recording,” he said. “Losing Malcolm, the thing with Phil and now with Brian, it’s a changed animal. I feel in my gut it’s the right thing