road bike needs better hill climbing gear ... I replaced the Ultegra cassette with a XT, no change to the chain or deraileru (105) ... now the drive train makes a funny chain noise, especially when the chain is on the larger cogs ... original chain is Shimano something ...checked the chain tension and the deraileur action - looks OK. Upper pulley is not contacting cogs. is the Ultegra casette interchangible with an XT cassette in terms of chain ?