21 Inch John Deer self propelled push mower with blade clutch.

I cannot pull the cord to start. Very difficult, and you sort of hear a grinding noise when you can pull it. I just put a bungee cord on the blade engage lever and I can now turn the engine with the pull cord. I assume the blade is turning too. I haven't tried starting it this way because the mower is in the garage and it's raining outside. Anyway, what is likely the problem? I've read some about replacing the blade clutch. How do I know if this is the issue? Also, there are different parts of the clutch. How do I know which ones to replace. I don't see much buildup of grass underneath that could be messing things up. Thanks!