'Rubber hoods' implies that you have Ergopower shifters or integrated brake/shift levers. These 8-speed shifters only function correctly with Campagnolo rear derailleurs made from 1992-2000. So if you really have (any) Shimano rear derailleur and any 7 or 8, 9 or 10 speed cassette (by any maker), they will not work together. The chain will constantly jump and rattle around randomly; some riders think this is normal.
There is a good chance the right lever needs an overhaul, which is an hour-long job for someone experienced. Or a frustrating scary challenge for the first timer. Parts cost: about $100 for the parts: the hoods, G-spring carrier and G-springs. The left lever never needs overhauling.