Check the trans fluid for contamination, flush it out & replace with new fluid,if it has only just happened the trans may be ok, The contaminated fluid will delaminate the clutch plates & coolant corrodes the solenoids etc. How old is the car & how many Kms. I had the same problem with my BA & had radiator ,trans ,hoses, overfloww tank replaced & flushed out the engine. I fitted a cooler & by passed the radiator. The car had only done 118000Kms ,4 years old.