727 manual valve body-Reverse is slipping BAD, All other gears seem good - Pressure tested

Does it slip on first engagement into reverse after starting the engine? I and a number of others have experienced this on 904's. start cold engine, put in reverse and the trans acts like it is slipping really bad, put in neutral and give a bit of gas, let off and put in reverse again and it feels good. seems to be typical for 904 don't know if the other trans does same thing.