12:30 PM PT -- Tesla says they've investigated DeWitt Lambert's complaint, and the other employees involved told a much different version of events leading up to the recording showing them using the n-word. In fact, Tesla says they now have personal instant messages where Lambert not only uses the n-word ... but says he was seeking revenge on his co-workers.

Bottom line: Tesla says they've suspended Lambert, with pay, while they reopen the investigation.

An African-American man who worked for Tesla claims he was harassed by other employees and called the n-word.

DeWitt Lambert filed a federal lawsuit, claiming he started working for the car company in 2015 and served as a production associate. He says the harassment began almost immediately. It started with hazing type stuff -- putting stickers on his back, putting nuts and screws in his pocket and hiding his tools.

Lambert says things escalated a few months into the job and he got a menacing recording on his phone ..."N****r, we take your ass home, n****r. Shred you up in pieces, n****r. Cut you up n****r, send your ass [to] everyone in yo family so everybody can have a piece of you, n****r. Straight up, n****r. We get down like that, n****r."

The lawsuit also claims employees humiliated him, sticking a drill gun in his butt while he was bent over. They also routinely made comments about the size of his penis.

Lambert says after he complained, some of the alleged harassers were actually rewarded with a promotion.

He's claiming discrimination, a hostile work environment and wants an unspecified amount in damages.

We reached out to Tesla ... so far no word back.