transmission trouble.
My 1969 chevelle malibu it has a 327 with a powerglide transmission, I notice that when I start the engine and select drive it won't engage unless I acelerate at high rpm,and sometimes will engage, the same with happen when select rear drive. I chage fluids and filter screen.....
if it has vacuum control on side replace it and check hose for running vacuum ,also kickdown rod must be adjusted if it exists from throttle linkageto trans, all work with control pressure, band apply, downshift,ect.
the stall on your tourque conveter is your problem
i say its a valve body check valve/string..add a pint of gas treatment run it a short while running between all the forward/reverse gears..you can also run type f fluid in it..its better than dex..but not dex in a ford..
