Allison Transmission Questions icrman, Is there a reason you want to know this? LOL. In the valve body you have trimmer valves (which has to do with how soft or firm you want shifts), relay valves (2) shift valves and hold reg valves. If you your question easier. It would be very difficult for me to explain without the diagrams here or there to explain and really, maybe its just me because I know other mechanics that use these hydralic shematics, but I rarely need to. Sorry if I cannot explain maybe if you asked a general question on your operation, I can answer those much better. Thank you though for the question and have a wonderful holiday!