So I'm looking through the Toyota EPC for 3S flywheel part numbers, and I find 2 parts listed:

13453-74011 Gear, Flywheel Ring 5SFE, 3SGTE..ST18#..MTM
13405-74080 Flywheel Sub-Assy 3SGTE..ST185
13405-74120 Flywheel Sub-Assy 5SFE..ST184..MTM

I thought the flywheel was on our cars is one piece, is it really a sub-assembly or does the sub-assembly include something else? I have no idea what else it would come with though, bolts maybe?

I saw that flywheel ring gear was the same for 5S and 3S motors and told someone to go ahead and use the 5S flywheel with his 3S motor. Apparently it didn't fit. Oops.

the ring gear is press fit into place onto the flywheel.
its what the starter engages to start the engine.