Topic: 90 mustang lx auto trans shifts weird????

[mustanglx5.0]

i have a 90 mustang lx 5.0 auto
everything was running good before the rebuilt,trans was shifting and it was running good.
then during the winter i decided to take the engine out and rebuilt the engine
after the rebuilt i put everything in and got it too run
connected the trans bolted everything up; but
its running good, but the transmission is shifting weird
could it be a linkage to the auto trans that i didn't connected it right,or do i need to rebuilt the trans now?
throw me some ideas id appreciate it thanks

[mustanglx5.0]

vacuum modulator idk what that is?
also what does that do for the trans. the trans is shifting slowly and goes to high gears with in 20 to 30mph?
also the trans is leaking some oil?