Image imprint Devil's Due had begun a new GIJoe series in 2001, to considerable acclaim and success. The following year, Dreamwave enjoyed huge sales with their Transformers Generation 1 series. It was probably inevitable that a crossover would be mooted. In fact, two would appear, one published by each company.
Devil's Due's was the first to appear, featuring Cobra finding the Ark and enslaving the Transformers. It was penned by the company's GIJoe writer, Josh Blaylock, with art from Mike S. Miller, formerly of JLA and assorted Marvel titles.
Boosted by no less than six cover variants, the series got off to a superb start sales-wise, with the first issue registering as the 7th biggest seller in ICv2's Top 300 charts, with over 98,000 copies estimated to have been sold. However, for #2 sales fell by a third, and after a slight boost for #3, declined until the end of the series, ending below 50,000 estimated sales, despite a number of variant covers, including a 2003 OTFFC exclusive cover.
Reaction to the series was mixed from both Transformers and GIJoe fans, but Devil's Due, now independent from Image, decided on a sequel. GIJoe vs. the Transformers II was a four-part series, following the same continuity. The first issue emerged in September 2004, with the plot featuring various GIJoe and Transformer characters scattered around various time periods. Dan Jolley had taken over scripting duties, with E. J. Su and Tim Seeley starting on the art chores, with Emiliano Santalucia and Guido Guidi later helping out. Sales were notably poorer than the first series, as was the fan reaction. The series had a sequel-hunting conclusion, but as Devil's Due bid unsuccessfully for the Transformers license after Dreamwave went bust, further crossovers don't currently seem to be on the cards.
Addendum: following the obtainment of the Transformers license by IDW, a third volume, titled "The Art of War" was approved. This five-issue series began publication in 2006, followed in first quarter of 2007 by a fourth volume, "Black Horizon". This seemingly concludes Devil's Due's involvement with Transformers comics.