I could take the input and output shafts on my bike, dump all the gears, spacers, snaprings, and bearings into a box and reassemble them in less than 2 hours. However, I really have no idea how automotive automatic transmissions work. I bought a 84 Chevy Nova from some girl for $300 bucks. It didnt run when I bought it, but I fixed it up to the point where it runs fine. However, I figured it would be a good idea to change the trans fluid and filter in it. I took it to a Cottman Transmission joint because I had a coupon for a $15 fluid change. They of course told me that I needed a "transmission refurbish" which would cost over $600. They told me that it would be a bad idea to even change the fluid in it because the detergents in the Dexron Mercon 3 fluid would accelerate wear to the friction plates in the transmission. In fact they said that they are borderline about changing just the fluid because they dont want to be responsible for my transmission unless they can rebuild it at the same time. Are they serious about this? I dont understand how they could say that new, fresh, fluid would accelerate wear on my transmission, especially when the service manual for the car says it should be done every 30k miles.