When they butted their chests in “Fast Five,” movie hardmen Vin Diesel and Dwayne “The Rock” Johnson — or rather their onscreen characters — almost ended up taking out half of Rio.

So it could be time for Hollywood to batten down the hatches, because the film industry’s most macho musclemen appear to have beef in real life.

It all started when Johnson, 44, posted an emotional rant Monday on his Facebook and Instagram accounts, referring to some of his male co-stars on the shoot of “Fast and Furious 8” as “candy asses.”

“There’s no other franchise that gets my blood boiling more than this one. An incredible hard working crew,” he said, praising the professionalism of his female co-stars in the action franchise.

“My male co-stars however are a different story. Some conduct themselves as stand up men and true professionals, while others don’t,” the former wrestler went on.

“The ones that don’t are too chicken to do anything about it anyway. Candy asses. When you watch this movie next April and it seems like I’m not acting in some of these scenes and my blood is legit boiling — you’re right.”

Johnson didn’t name names or say what was riling him, while Diesel, Jason Statham, Scott Eastwood and rapper Ludacris have refrained from responding.

But the gossip website TMZ — citing unnamed “production sources” — reported that Diesel was the target of the tirade, and that the pair had a secret meeting on set in Atlanta Tuesday to “hash things out.”

“We’re told The Rock has butted heads with Vin during the production, in part because V.D. is a producer and has made decisions that didn’t sit well with the former wrestling champ,” TMZ said.

Meanwhile an insider was quoted by E! News as saying that filming “wasn’t easy for anyone” and had been especially difficult for Johnson, who is also a producer on the movie, which finishes filming in a week.