Here is the breakdown about the T-20......its a pretty bulletproof transmission. I have taken apart units that were 35+ years old and they still looked like new inside. They are pretty easy to rebuilt and are really well designed in my opinion. There have been some slight variations in the T-20 units that have been built over the years so if someone wants to jump in and keep the ball rolling here, please tell us about them for anyone who may be curious.