[Spd] is usually associated with Engines, rather than shields.
I'm not sure whether it was intentionally added to the list of possible mods on shields or not. We have seen engineering mods on high end sci consoles and vice versa, so it might have been done on purpose.
If it was added on purpose it doesn't work.
I crafted a bunch of Mk2 gear to use on a new toon to level up and upgraded it as I levelled.
It was only once I'd got a few levels and got lucky in rarity upgrades on the shield that i started to investigate what i was getting for my [spd] bonus.
Screenshots show the "movement" section of the ship stats with the shield on and off.
http://catsgopurr.com/STO/shield-on.pnghttp://catsgopurr.com/STO/shield-off.png
Comments
...but it didn't remove/replace the [Spd] mod nor did it make the mod functional on a shield I got off the exchange to test. It retained the [Spd] mod after the character copy and following upgrades from Mk II to Mk X.
As it stands, your shield will continue to have effectively one less mod than it should.