Former England defence coach Mike Ford has also joined the club's backroom staff as the club look to avoid relegation.
Tait had admitted he was considering his future after defeat to Exeter had left the Falcons adrift at the bottom of the Aviva Premiership.
However he has now decided to 'take a break from rugby' - with forwards coach Paul Moriarty taking charge of this Sunday's Amlin Challenge Cup clash with Petrarca Padova.
Club owner Semore Kurdi said: "I would like to welcome Gary and Mike to the club. They will be a great asset alongside the existing coaching team and this is a demonstration of our intent to fight back and secure our Aviva Premiership status."
Gold arrives at Kingston Park having spent the past four years working as assistant to Peter de Villiers in the South Africa set-up.
Gold cut his teeth coaching at London Irish, having joined the backroom staff at the Exiles in 2001 before stepping up as head coach.
After returning to South Africa, Gold went on to work with the Stormers and Western Province.
"This is an exciting challenge and I am delighted to have the opportunity to work in the Aviva Premiership," said Gold.
"Newcastle Falcons is a big club with big ambitions and an owner who is very determined so anything is possible.
"I know a lot about the players and the traditions of the club so I am really looking forward to the challenge of keeping top-flight rugby in the north east."
Ford will also bring a wealth of experience with him having worked with Ireland, Saracens and the British and Irish Lions before joining the England set-up in 2006.
Ford, a former Great Britain rugby league international, left his post with England in 2011 and had been assisting Leeds on an ad hoc basis.
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