Bases on a tip in a forum 1), it is possible to replace the internal noisy 3,5„ HD with a silent SSD.
The replacement is straight forward. Just remove cable and unmount the old drive. Mount the mobile rack with the two screws towards backside within the original holes, for the two screws towards fron you need selfthreading screws. On the SAK-65 Adapter a missing hole has to be drilled, see image:
https://www.flickr.com/photos/pisco_cgn/13494599864/in/photostream/