I know this is an old thread but I just thought I would throw in my 2 cents. Since completing a 15-year nut and bolt restoration on my Z I've put about 1100 miles on it. Every drive train component on the car was rebuilt. Generally, the car drives very well but the shifts are "notchy". I wouldn't even dream of power shifting it due to a total lack of smoothness shifting the Muncie. At first, I thought maybe the synchros weren't right but after doing a little reading (including this thread) I just ordered 2 quarts of ACDelco Manual Trans Fluid 10-4070 75W-90 GL-4. I will post again after I change the fluid and let you guys know what change there is (if any).