Retière spent the last four years working as the forwards coach under Marc Lièvremont helping France to the Grand Slam in 2010 and a World Cup final last season.
But having moved back to working in the national youth development (DTN) system, Retière will now spend time with Racing where he will reunite with former France kicking coach Gonzalo Quesada who is the backs coach.
He said: "The Under-20s would have been enough for me. But it's nice to keep a link to professional rugby. It's a short experience until the end of the season. After that it will be up to me to decide if I want to get into pro rugby full-time, maybe with Racing, or if I stay in the DTN.
"It was the best solution for everyone involved with my commitments to the federation, but also for the club. The season is underway and everything is in place. It was quite easy to find an agreement.
"It's true. Gonzalo and I have a few links. Racing is my old club where I played when I was young. Several things played a role. It would have been more difficult if it had been another club. But the closeness of Marcoussis made it easy.
"We'll have to work on what has already been done. There will not be a revolution.
"I'm happy to join in this role, that is a consultant for one session a week. It was an easy decision."