difference between flywheels?

is there a difference between 2001 and 2002 mercury cougar flywheels for an automatic transaxle it has 2.5 liter v6 replaces engine with 2001 engine but used 2002 flywheel ,replaced transaxle with 2001 rebuilt transaxle 6months later, but after bolting up torque converter to flywheel front seal really leaks like torque converter was pulled out of seal