I recently filled my car up with the same stuff: tranny and diff. I was not able to get an apples to apples comparision with Redline, since I jsut put in a new tranny. But I feel that the amsoil causes the tranny to be a bit notchy. And that I might be able to get some more smoothness out of redline. Don't want to drop and fill with Redline if it won't help though. Since the fluid has less than 1000 miles on it.