If it's leaking in just one general area on the Y pipe where it is accessible, try getting a muffler wrap kit. They sell them at Checker, WalMart, etc. Usually it is a metallic or fiberglass type tape that you wrap tightly around the leaking area. As it gets hot it shrinks and seals up somewhat around the area. It may help quiet it down but it is only a shlock fix until you get a proper repair completed.
Randy Rosetta KDØKWX TLCA #19351 69 FJ40 "Meanie" & 1970 Boss 302 Mustang