CREATE TABLE table_23120 ("Fleet #" TEXT, "Year" FLOAT, "Manufacture" TEXT, "Model" TEXT, "Length  ( ft ) " FLOAT, "Engine" TEXT, "Transmission" TEXT)

Which year had a transmission of Voith D863.4 and a Cummins ISM engine?
SELECT "Year" FROM table_23120 WHERE "Transmission" = 'Voith D863.4' AND "Engine" = 'Cummins ISM'
SELECT "Year" FROM "table_23120" WHERE "Engine" = 'Cummins ISM' AND "Transmission" = 'Voith D863.4'