Originally Posted by
miamijim
7400, 7401 and 7402 RD's will work with 7400 STI levers. I'm not sure if the 7400 has enough travel for 8-speeds but it will properly index. Keep in mind that all you need to do is match the first two numbers to play it safe:
74XX derailleurs only work with 74XX levers
77XX and 78XX derailleurs will NOT work with 74XX levers and vice versa
77XX and 78XX levers will NOT work with 74XX deraillers and vice versa
Here is a question for you: Will 77XX derailleurs work with ST-6400 STI levers? (Assume a 8sp cassette). Everywhere I read, I assume that this is the case, but have never actually seen that combination at work