yup it's a 4l80e. my 98 say 4l80e heavy duty but i don't know if there is a real difference. i just turned 100 g's and it still pulls strong. but i am thinking about a good tranny tune-up soon. pulling 13k with that rig will be okay, you will know it's back there and it slow down to 50 mph or so on up hill grades but you will get there. oh and don't tow in OD.