I did exactly what you did with my 2009 24" IMac.
There is a thermal sensor attached to the hard drive, and when you do an SSD upgrade, the fans spin at full speed as they think the hard drive is overheating. I know you can do one of three things:
1) You can buy a kit from OWC (it is bundled with an ssd and a lot of tools) - so EXPENSIVE;
https://eshop.macsales.com/item/OWC/KITIM09HE2TB/
2) You can "short out" the hard drive temperature wire and it may stop the fans from running full speed;
http://blog.macsales.com/19617-diag...ed-issues-after-upgrading-the-main-hard-drive
3) You can install a program called SSD fan control, allows you to manually control the fans. This is what I did personally on my 09" and it works great.
http://exirion.net/ssdfanctrl/