'South Beach Tow' Star Robert Ashenoff -- Gruesome Gash After Spinal -

"South Beach Tow" star Robert Ashenoff underwent spinal fusion surgery and he plans to use this picture to pry a fortune from producers who he claims are responsible.

TMZ broke the story ... Ashenoff will sue the production company which is owned by Jennifer Lopez -- claiming honchos ordered co-star Larry Diaz to surprise attack him on September 8, 2012 ... all as a ploy to goose ratings.

Ashenoff believes the scripts and raw footage will make his lawsuit airtight ... so he wants a judge to force producers to hand over the goods.

Ashenoff says he's undergone spinal surgery because his injuries were so bad -- and we're told the 13-hour procedure was gruesome -- 16 screws in his neck. Total hospital Bill: $800,000.

We know the production company insists Diaz didn't intend to harm Ashenoff (think WWE style) ... he just went overboard and the elder Ashenoff took a weird tumble, seriously injuring his spine.

Producers decided against airing the footage -- they were probably scared of a lawsuit. Ashenoff later appeared on the show wearing a neck brace ... which the show claimed was the result of a car accident.

We're told producers have since decided to 86 Ashenoff from future episodes.