Thomas Bernard Downey, 74, of Cranford died yesterday at home.      A Mass will be offered at 9:30 a.m. tomorrow in St. Michael's Church, Cranford.  Arrangements are by Gray Memorial Funeral Home, Cranford.    Mr.  Downey was the owner and president of Essex Travel Service, with offices in Cranford and Newark, for 32 years before retiring in 1988.

He was a member of the Cranford Chamber of Commerce and the American Society of Travel Agents.  Born in Orange, he lived in Cranford for many years.  Surviving are his wife, Barbara;  two daughters, Mrs. Barbara McCullough and Mrs. Mary Ann Sacko, and a sister, Mrs. Mary Langstaff.