This phase I/II trial is studying the side effects and best dose of sorafenib, gemcitabine, and capecitabine and to see how well they work in treating patients with unresectable and/or metastatic kidney cancer. Sorafenib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth and by blocking blood flow to the tumor. Drugs used in chemotherapy, such as gemcitabine and capecitabine, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving sorafenib together with gemcitabine and capecitabine may kill more tumor cells.