A rocky relationship.

Sylvester Stallone claimed he threatened to knock out Richard Gere’s teeth during an on-set argument while filming the 1974 film “The Lords of Flatbush.”

In his new memoir, “The Steps,” Stallone wrote that he and his co-star didn’t get along from the start, and bad blood started to form during the audition process, when they disagreed on an ad-lib session.

During the session-gone-wrong, Stallone alleged, “Gere grabbed my T-shirt and his fingernails dug into my skin.”

He continued, “I told him to back off, but he did it again on the second take. He couldn’t have known, but Gere had begun to stir the emotional cauldron inside me.”

In response, Stallone asked director Stephen F Verona if he could ad-lib and “react the way [he] would actually react if someone did that to [him] in real life.”

When he explained that his reaction would be to knock his teeth out, Verona allegedly replied, “Please don’t.”

The 80-year-old continued in his book that their relationship deteriorated even further as filming picked up.

According to the “Rocky” icon, Gere spilled chicken grease over him during a lunch break, triggering a physical confrontation so intense that the director had to put himself himself between them.

“A stream of chicken grease spilled off the foil paper onto my leg. I elbowed him across the chest, got out of the car, came around to his side, and pulled him out of the back seat,” Stallone recalled.

“Hey, man, I don’t want to get physical,” the “Pretty Woman” actor purportedly pleaded in what Stallone characterized in his book as a “thin voice.”

“Too late…,” Stallone claimed to have replied, only for the altercation to be broken up by Verona placing himself in front of Gere.

“It was clear to everyone that this wasn’t working,” Stallone wrote. “One of us had to go.”

Ultimately, one of them did go, as Gere was replaced by actor Perry King. 

Page Six has reached out to Gere’s rep for comment.

Directed by Stephen F Verona and Martin Davidson, “The Lords of Flatbush” follows a group of street teenagers in leather jackets from the Flatbush neighborhood of Brooklyn, New York.

The main cast includes Stallone, King, Paul Mace and Henry Winkler.

“The Steps” is now available wherever books are sold.