I put a 12tz in my rush, I swap it back and forth between the rush and rustler. I pretty much just slid right in. If I remember right, the 18 and 12 havethe same distance between mounting holes so you should be fine. What kind of shaft did you get? That would be the only thing you should have to worry about. 1.9 hp out of the 18tz, in a rc10 gt, sweet. Hope you ordered some tires too, my 12 eats them up.