loose cv shaft

The front right cv shaft on my 80 brat is very loose on the shaft on the trans and it makes a thunk sound when i let off the clutch. I havent taken it apart yet so i don't know if the output shaft on the trans or the cv joint is worn (or both). Now, if the output shaft on the trans is worn would i be able to replace it without takeing the whole trans apart? is there any other way to fix this?

Thanks

mexiburger