Walls and Ceilings - Building a Wall in the Garage . . .

I'm building a wall to seperate the single car garage from the two car garage. The wall will be built parallel to the floor joist.
The wall will be in between the floor joist (within 8" of one of them). My question is, how do I secure the top plate when I have nothing to nail to?
My thinking is to put up a 1 X 8 or 10 nailed to the joist and then secure the wall to the 1 X 8?
The wall existed before I bought the house (model) and I'm putting the wall in the same location as it existed before but the folks used the metal studs and installed the top plate into the sheet rock . . . not working for me.
If someone has any better idea as to how to attach that top plate, I welcome your suggestions.
Thanks for your time and consideration.
windancer

Welcome to the forums!

If I understand correctly, the best way [imo] would be to remove part of the ceiling so you can insert nailers between the floor/ceiling joist. You would then drywall the ceiling along with the wall.

I am hoping you meant "ceiling joists", and I hope the floor is concrete. With that out of the way, what Marksr said is the correct way to install the wall. But, since it is not load bearing, and if you have access to the ceiling area, place your nailers across the space between the two joists on top of the sheetrock ceiling and attach your top plate, or wall assembly to the cross members. I am a firm believer in wood to wood contact, as even plywood will compress, and surely sheetrock will. But in your case, as long as it is just a screen wall so to speak, you can do it without problems.