The car salesman said farewell in a YouTube video titled "This Is Goodbye (RIP 7/27/79 - 8/25/24)" ... and his videographer confirmed his death in the comments, writing, "I am with him now in Hospice. He just passed at 21:45 on 08/25/2024. He will be missed and we will never forget him!"

In his text-based farewell video, Rob shared he felt "off," and started experiencing symptoms like weight loss and acid reflux while filming "Tex Mex Motors" season 2 ... which his doctors finally diagnosed as stomach cancer.

Rob explained since his diagnosis, things have been tough while he’s been receiving treatment at home ... with more bad days than good.

He ended on a positive note, reflecting on his achievements, including marrying the love of his life ... while also urging fans to never ignore their health concerns, encouraging everyone to seek answers if something feels off with their bodies.

Rob shot to TV fame last year on the reality series ... alongside Marcos "Scooter" Carrera ... where they scouted vintage cars in Mexico and transported them to El Paso, Texas, for major transformations.

Pitts is survived by his wife, Randi Foraker, and his mother Kim Pitts.

Pitts' family said in a statement: "Since Robby's passing, the outpouring of support for the family has been incredible. We are not surprised that his stories touched so many - we had no idea of the depth of each connection he made. We wish to thank his friends and fans for keeping these memories alive and showing the impact of the work he did that always came from his heart.”

He was 45.