This is a known failing of the neoprene bushes that mount the remote mechanism to the gearbox. Essentially the perished bushes allow the bottom of the remote to contact the prop shaft. The misalignment compromises the change quality and the noise is the result of the contact.
Replacements are available from Rimmer Bros. Replacement involves removing both seats and the gearbox tunnel cover and changing the bushes. Reassembly involves repeating the process in reverse.
Hope this helps.
