Chosen Solution
I have done everything that i learned here on how to switch the HD on my iMac to a SSHD bought here at ifixit. In fact it’s easy. The problem is the iMac don’t recognizes de SSHD and i cannot install the MAC OS X. Then i get back to the HD and there it is, works well. Do i need to format the SSHD outside of the iMac to make it work? Thank you Update (09/26/2017) I bought this one, is exactly the same of the original previously installed: 1 TB SSD Hybrid 3.5" Hard Drive
I usually format the drive and install a system externally. If I don’t do that, then I drop the drive in and boot from an external drive, then format it and install the system from my external. I’ve done dozens of these drives in these earlier iMac with excellent results.
