vx ss auto trans problem

[snowy213]

hey ive just had my head gaskets done ansince iv had the car back my auto trans has been playing up mite just be a coinsidience or they mite have coursed it do these autos have a vaccum line it.
it revs out doesnt change till about 4000rpm any one with any ideas trans fluid level is good do trans fluid get thined out like oil does??or myb just needs a tune any ideas on how much a tune is for a auto trans?? any help would be great