4T65E:
1998-2003 Pontiac Grand Prix V6 3.1 L/3.8 L
1997 Pontiac Grand Prix 3.4 DOHC V6

4T60E:
1993-1999 Pontiac Grand Prix "GT" 3800 V6 (L36 Motor)

Up to 99 some cars with the 3.8L had the 4T60E. My buddy's 98 has the 4T60E