Hey there fellow Garageband user, Mr. NE! The drums are all modern 808 from beat sequencer, I just wiped whatever default pattern they have and build on top of that. The sounds from the kit I ended up using are: Kick, Closed Hit-Hat, Clap, Low Tom, and Bongo. For sub-bass I used Crushed 808 Bass - Raw 808 from the Alchemy Synth option under Keyboard (if I interpreted it correctly). I'll give yours a listen in a moment!!