I picked up a free transmission with a broken syncro that I want to use in my 91 Miata street car. The donor was free and the person I got it from had no idea what it came out of. My understanding is that a 1.8 transmission will work in a 1.6, but how do I tell what my donor is? Is there a difference between the 1.6 and 1.8 transmission? It seems to be the question asked of me when ordering parts. I was told this transmission was grinding going in to 2nd which is what my street car is doing. My car is still drivable so I want to repair the donor first. Any help is greatly appreciated.